c 71 1

111. Notes on the Development of the Ooula of Loranthus and Viscum, and 012

By WILLIAM GRIFFITH, Esq., Communicated by R. H.

the Mode of Parasitism of these two Genera. Assistant Surgeon in the -Mudras Medical Service. SOLLY, Esq., F.R.S. & L.S.

Read June 21st, 1836.

1 SHALL take as the type of the evolution of the ovula those of Loranthus Scurrula.

At the earliest stage, that I have submitted to examination, I find that the ovarium is intimately adherent with the parietes of the calyx ; its shape being merely indicated by lines of a denser tissue than the rest. The broadest part is situated towards the apex of the tube of the calyx. I t is hence prolonged upwards, and terminates by being continuous with the tissue of the base of the style. It is prolonged likewise downwards into a long subulate process, which is continuous with the tissue of the pedicle. In the centre of the broader part a transverse opake line of tissue is visible. The tissue composing the calycine parietes is nearly homogeneous; nor is there any rudiment whatever of a viscous formation". If we examine a flower shortly, or even immediately, before expansion, we find that in addition to the above, there is a brown, as it were, sphacelated line which runs along the centre of the style and the upper prolongation of the ovary to the centre of the transverse opake line ; here it is thickened, and either ceases or spreads transversely on either side in the direction of the opake line. At this part there is evidently a small swelling, and the tissue has become more transparenti-. These two changes are owing to the commencement of an excavation formed by the dislocation of the originally continuous tissue, and which communicates freely with the canal apparently existing in the style, along the sphacelated line. Almost simultaneously with the appearance of this excavation the formation of the

* See Tab. IV. fig. 1, t Ibid. fig. 2.

72 MY. GHIFFITH on the Development of

viscous tissue commences, which is, even in its early stages, of a green colour. Just after the fall of the corolla no change of any importance has talien place. There is a greater development of the viscous tissue, and the excavation is larger and nearly filled with broken-up tissue. The canal leading from it appears diminished, but is still distinct. Some time after the fall of the corolla we find the excavation is considerably increased and partially occu- pied by broken-up tissue *. The viscous tissue is considerably developed, and the greater part of it contiguous to the ovarium lias become of a beautifully rich green colour.

Soon after this a small cellular body appears attached to that part of the excavation immediately opposite to the termination of the sphacelated line. This is the rudiment of the ovulutn. When the fruit is about half formed the above parts have only undergone an increase in size. Both laycrs of viscous tissue are well developed, the green one being in intimate contact with the ovary. The ovulum is between cordate and ovate, its circumference being tinged with pink ; and it now has the appearance of albumen. Occupying a niche in its centre we observe the young embryo. It is at this period totally included in the albuminous-looliing body, and is suspended by a flat cellular funiculus from the part of the envelope, corresponding to the termination of the sphace- lated line; it is oblong, cellular, and presents no trace of cotyledonary di- vision t.

As its deve- lopment proceeds, the division of the cotyledons becomes manifest, and SOOR

extends throughout rather inore than half of its length:. The funicle equals it in length, and is as well as the embryo itself entirely cellular. As i t advances in size the embryo ceases to be oval, and appears as if pulled out into a more elongated form, its base or radicle becoming a t the same time thickened. The division of the cotyledons continues to be apparent for some time, but ceases to be so at length from the adhesion of their contiguous faces. There is, how- ever, always a certain degree of obliquity at their apices, which enables us to recal their original separation. No union takes place by their irnrnediate bases 0.

The base or termination of the sphacelated line is still distinct.

The subsequent changes are confined chiefly to the embryo.

* See Tab. 1V. fig. 4. 1. Ibid. fig. 5. 4 Ibid. fig. 6 . Q Ibid. fig. 8 & 9.

the Ouula of Loranthus and Viscurn. 73

The fully developed embryo is oblong, clavate, the radicle forming the thickest part; there is a slight narrowing about the junction of the cotyle- dons with the radicle. I n the centre of this part two oblong foveolae or sulci are observable, which owe their existence to the non-union of the bases of the cotyledonsx. The pluniula is small, but totally concealed, unless indeed the cotyledons are cut away. The embryo is attached very slightly by a very fine short membrane, the originally long funicul us having disappeared. This dis- appearance is, I imagine, not real ; probably the tissue of the funiculus contri- butes to the formation of the embryo. The coloration of the embryo keeps pace with its development. Throughout its first stages it is colourless; the green colour is first visible about the time that the division of the cotyledons appears, and it continues increasing as the embryo approaches nearer and nearer to a state of perfection.

At this time it is entirely green, the colour differing however in tint ; the radicle, particularly towards its apex, being tinged with yellow. The greatest development of green is a t the base of the cotyledon, about the sulci or clefts.

With respect to the changes that have taken place at the time of maturity of the fruit in the calyx and ovarium, I must mention the total disappearance of green viscous tissue. The whole cellular substance between the outer layer, 01' cuticle of the calyx and the ovarium, is converted into a yellowish transparent viscous matter. This is not, however, prolonged down the stalk of the ovarium, which is now fibrous-/.. With respect to the ovarium, the only remarkable circumstance is the softening down and conversion of a portion of its texture, particularly towards its apex, into viscous tissue. This often occurs to such a degree that the naked radicle is imbedded in the viscous tissue, and is no doubt intended to remove any impediment to the occurrence of germi- nation.

I n two or three other species that I have examined the same phenomena occur ; but in these there was no development of green viscous matter, nor any colouring of the albumen. I n one species the cotyledons were consoli- dated, and two natural clefts existed ; in the other, they were merely applied face to face, consequently no clefts were present or necessary. But inde- pendent of these, and of changes of form dependent on specific difference, I

* See Tab. IV. fig. 9. 1 See Tab. V. fig. 1 . VOL. XVIII. L

74 i%!r. GRIFFITH on the Development of

observed the same complete adhesion of the ovarium and calyx ; the same ori ginal solidity ; the same subsequent sphacelation visible along the centre of the style, and terminating at the site of the future excavation; the same excavation; the same subsequent appearance of the ovulum ; the same formation, inclusion, cotyledonary division and evascularity of the embryo; the same apparent short- ening and almost total disappearance of the funiculus ; the same nudification of the apex of the radicle ; the same degree of coloration, and the same softening down of the ovarium. This in one species is carried to such an extent that only a portion of the base of the capsule remains in its original fibrous state ; so that the greatest part of the albumen and immense radicle are enveloped by the viscous tissue *.

Ovvla of Viscum.

In the earliest stage at which I have been able to examine the ovulum, I find a similar adhesion of the ovarium and calyx. The outline of the former is distinct, and the communication of its apex with the central canal leading from the base of the style open and very freet. There is no development of viscous tissue. Towards the apex of the ovariuxn there is a cavity communi- cating with the canal leading from the stigma containing a cellular, mamniil- liform, central, but not papillose body, attached by a broad base, its apex touching almost the termination of the canal. This is connected inferiorly by a thickish opake line running through the centre of the ovariurn to its base. This line is evascular, and consists merely of rather dense tissue. At this period the nipple-shaped process, as I may call it, is brownish$

No important change occurs until after impregnation ; the only interme- diate ones being the diminution of the diameter of the canal, and its greater length after impregnation, so far as niay be judged of by the sphacelation of the stigma, the process is very apparent; it is enlarged, and its apex more attenuated. From the base of the central line, which runs from the base of the process to the corresponding portion of the ovarium, two brown lines are apparent, curved upwards and outwards. These lines are of a much deeper brown than the rest of the process ; corresponding to one of the terminations of the curved lines there is a small lateral excavation, which is partly occupied by broken-up tissue, partly by a sac which is attached to, and hangs from that

* See Tab. V. fig. 5 & 6. f Tab. X. fig. 1. $ See Tab. X. fig. 1 , 2 & 3.

the Ovula of Loranthus and Viscum. 75

part of the process corresponding to the termination of the curved line#. This sac consists of a single cell or vesicle enclosing many grumous, opake, ovate, or angular bodies; it has a broad attachment, and is the rudiment of the ovu1um-f.

As the development proceeds the viscous tissue increases, the sac enlarges and becomes cellular, and its attachment narrower. I t soon assumes a broadly- obovate form, its attachment becoming at the same time exceedingly narrow. At this period a vesicle is seen inclosed within the tissue at the commencement of its narrow neck$. This tissue soon assumes the appearance of albumen. The viscous tissue is well developed, occupying the whole of the apex of the fruit (the prolongation of the canal remaining isolated in its centre), and extending to the base of the fruit, to which point it gradually narrows. The figure of the ovarium has changed, four or five prolongations beginning to appear towards its apex. No change has taken place in the process, and the two brown curved lines are still visible. Its stalk, as the albuminous-looking ovulum enlarges, becomes pushed on one side. The ovulum reaches a con- siderable development before any change in the embryo occurs. When its cornua begin to appear, the embryo is globular, cellular, exceedingly minute, and attached to the nipple laterally. It is not entirely enclosed, but lodged in a cavity in the albumen$.

When the fruit is about half developed, the parietes of the ovarium are in- durated, and its prolongations are very distinct. The ovulum, which has for some time assumed the appearance of albumen, and the form of the ovarium, has 4 or 5 horns corresponding to the prolongations of the former, and as many obtuse angles. The stalk of the process has become detached from the surrounding tissue, except towards its base, and is pushed considerably to one side. The apex of the process is slightly elongated and papillose. The embryo has increased and assumed a more oval forin ; it has likewise become central, that is, it occupies the axis of the albumen. As the fruit increases in size, the embryo becomes unequally emarginate at the apex, indicating the first trace of a cotyledonary division\\. No further changes take place in the other

Simultaneously the viscous tissue has made its appearance.

* Tab. X. fig. 3, $ Tab. X. fig.4, 1) Tab. X. fig. 4. & Tab. XI. fig. 14.

L 2

t Tab. X. fig. 1. Tab. XI. fig. 10, 11 & 12.

76

tissues except in size. When the embryo is about half developed, the cotyle- donary division is deep, and the ratiicular end small ; but as the development proceeds, the cotyledons, which were always rather iinequal, become united, except at their immediate bases, corresponding to which sites two indistinct clefts may be found. At the same time the radicular end has become much enlarged*. Throughout its development the attachment of' the embryo to the process is slight, and very easily ruptured.

Finally, in the perfect fruit we find the viscous tissue occupying the whole space between the outer calycine layer and ovarium ; this is fibrous, somewhat indurated, obtusely 4- or 5-gonal, and prolonged upwards into as many points as there are angles. The albumen is colourless, fleshy, and of the same shape as the cavity of the ovarium ; the embryo is clavate, lodged in the apex of the albumen, beyond which and between its cornua the naked apex of the root may be seen to projectt.

The development in both the above genera is pretty nearly the same, if we except the want of the Inamniilliform process in Loranthus, and the unirn- portant circumstance of the attachment of the embryo of Yiscum being short. The following conclusions may therefore be applied to both.

1. That the calycine parietes are from an early period intimately connected with the ovarium, and that the whole tissue between the outer calycine layer and ovariuni becomes subsequently converted into viscum. 2. That there is a tendency, varying in degree, in Loranthus in the ovarinln

itself to become softened down into viscurn. 3. That in Loranthus the ovarium is a t an early period solid, as it is likewise

in Yiscum, if we look merely to the formation of the embryo. 4. That the ovulurn is formed subsequently to fecundation ; that its deve-

lopment takes place in a cavityformed by the excavation of part of the tissue of the ovarium.

5 . That the excavation commences as soon as the sphacelated line has reached the spot where the subsequent important changes are to be carried on.

6. That the first development of the embryo takes place a considerable time after that of the ovulum; that it is attached to tlie apex of this by a cellular funiculus ; that it is hence itself evascular.

Ah. GRIFFITH on the Deuelopnaent of

* Tab. XI. fig. 8 & 9. f Tab. XI. fig. 8.

the Ooula of Loranthus and Viscum. 77

$. That the embryo is a t first included in the ovulum ; that in Lomnthus the funiculus subsequently becomes very short, and the apex of the embryo naked.

8. That the cotyledons, in some, become subsequently united, except at their bases, and in such two lateral slits are visible externally.

General Remarks.

From what tias been stated, i t will appear that the ovulum is, both in Lo- ranthus and Viscuin, a formation subsequent to impregnation. This remark- able, and, I believe, unparalleled fact, will tend materially to increase the difficulty of understanding or even conjecturing the nature of the first steps in the formation of an embryo. It is evident that i t is at total variance with the idea that the ovulnm, or female organ, is a nidus adapted to, and necessary for the development of the embryo, which in this view is supposed to be derived entirely and directly from the male. It is needless to add, that it is totally different from the usual development of ovula.

With respect to the first part of the process of development, I may observe that original continuity of tissue is very general, and perhaps universal. And, in particular, I believe the nucleus of an ovulum to be ab origine solid ; what- ever is produced subsequently in its interior being developed in a cavity formed by an excavating process.

Although there can be no doubt from its structure and functions, that the fleshy body in which the mature embryo is more or less contained is albumen, yet it may be proper to state in what part of the tissue the necessary change is carried on ; particularly since there is, I believe, no instance of albumen occurring as a primary formation".

The albumen in both these genera may, therefore, be classed with those

* Although I have not proved the existence of a sac in Loranthus, within which the tissue which subsequently becomes the albumen, is formed, yet, from the consideration of Viscum, and from the obvious analogy which its sac presents to the sac of the amnios in ordinary structures, I have little hesitation in advancing the opinion that the ovulum in Loranthus and Viscum is reduced to its simplest possible state, and that the albumen is a deposit within the tissue of the amnios, the sac of which has at an early period ceased to exist, at least as a distinct membrane. Further researches may hereafter establish the fact of the amnios being the only essential part of an ovulum.

78 JZr. GRIFFITH oia the B e v e l o p e t i t of

alburnina which are developed in the tissue of the amnios and inclosed in an ordinary integument or integuments, with this obvious difference, that in the subjects under consideration this body is naked.

There is an evident resemblance between the nipple-shaped process of vis- cum, and the often stipitate, free, central placenta of SantaZacee, especially when more than one embryo is developed in the above genus*.

On the Mode of Parasitism.

The only species in which this has been studied in any detail is the Yiscum album, and even here the statements are not altogether satisfactory. The latest account which I have seen is that of De Candolle in his excellent Phy- siologie Ydgdtale, vol. ii. p. 790, and more fully in vol. iii. p. 1409, where the subject is treated in the usually luminous manner, so characteristic of this distinguished author.

The mature seeds of all the species of Loranthus adhere strongly to the substance on which they are applied by means of the viscous matter. This viscum soon hardens, and then has the appearance of a transparent glue. The first changes take place in L. Scurrulu two or three days after application, and consist of a curvature of the extremity of the radicle towards the sup- port ; this extremity when it reaches this point becoming enlarged and flat- t ened +.

I t has now the appearance of a sucker, such as those, for instance, of the Cassytha$Zformis. I am unable to state the precise manner in which the radicle penetrates the bark. The operation seems to require some time, and it is not until it is completed that the plumula begins to be developed. Tn those species the cotyledons of which are soldered together, the plumula passes out by one of the clefts; in the others by the fissure between these two bodies. The cotyledons in all the species I have examined remain in- closed in the albumen, which substance begins to disappear as soon as the plumula commences to be developed ; the cotyledons undergoing a corce-

* Compare the figures 2 and 3 of Viscum with that of the placenta of Thesium linophyllum.

-t See Tab. VII. fig. 1, 2, 3, 4&5.

Bron- p i a r t Sur la G6n6ration a'es V&gt?taux, Plate 43, fig, 3. B & c.

the Ovula of Loranthus and Viscum. 79

sponding diminution in size. By the time that the young plant is furnished with a pair or two of leaves the attachment will be found considerably firm. If we cut away the portions of the support, and lay bare the included portion of the parasite, we find that the application takes place entirely between the ligneous systems of both, the fibres of the sucker-like root of the parasite expanding on the wood of the support in the form of apdte d'oiex. There is, however, no interchange of structure between them ; neither at this period is there any intermixture of ligneous fibres. As soon as the young parasite has acquired the height of two or three inches, when a n additional supply of nourishment is probably required, a lateral shoot is sent out, which is, espe- cially towards the apex, of a green colour. This at one or two, and subse- quently at various points, adheres to the support by means of sucker-like productions, which are precisely siiriilar in structure and in mode of attach- ment to the original seminal one.

As the parasite increases in size, these lateral shoots become frequently very numerous, and give origin, 1 believe, always from those parts immediately opposite to the sucker-like adhesions, likewise to stems and branches. During the same period the fibres of the suckers become more and more imbedded in the ligneous system of the support, owing to the deposition of the new wood of the latter. The fibres of the parasite never penetrate beyond their original attachment, although the later developed fibres appear to have the power of arriving at this point, but no further. This is very remarkable. I n the adult plant the sucker-bearing shoots frequently run to a considerable distance, many of the stocks being literally covered with parasites, all of which have originated from one seed. I have seen such shoots, which had taken their course along a decayed branch, become reflexed, and return in quest, as I may express it, of a part capable of affording due nourishment. In all the species of Loranthus which I have examined the same phenomena occur, and also in the species of Yiscum from which the drawings were made. I have reason to believe, however, that in some Loranthi and Yisca the attachment takes place by one spot ; in other words, that there is only a primary attachment : such will approximate in form to the Yiscum album.

The sucker-bearing shoots frequently run contiguous to each other, and are

* See Tab. VIII. fig. 2.

80 Mr. GRIFFITH on the Developent of

occasionally reciprocally united by ‘‘ suckers ;” in such there is actual com- munication between the ligneous systems *.

With respect to the parts on which the parasitism occurs, J believe it is entirely dependent on the permanence of their nature. I have met with ;1 solitary instance of the attachment and evolution of Loranthus on the leaf of a Guttiferous tree. The plant had reached the height of two inches, and had developed several leaves ; no lateral shoot had been sent out. Its base was expanded on the upper surface of the leaf, and the sucker-like root had pene- trated the cuticle, and was firmly imbedded in the parenchymatous mesophyl- lum. Although in all probability this plant would, had it been left to its own fate, have perished, yet it might have become, before this had taken place, attached by a lateral shoot to a part capable of sustaining it by its permanent nature. I am also of opinion that attachment will take place on any plant?, or part of a plant, the duration of which is sufficiently long. Those with milky juice, though perhaps a general, are not an universal exception.

The juice of this species was not milky; it is hence obvious that they have an eliminating power, although the fact stated by De Candolle: of coloured fluids passing into their tissue through the stock would lead us to suppose cjther- wise.

With respect to the bourrelets formed round each attachment, they are occasioned by the deposit of new wood round their bases; they are often irregular, the upper part being, as might be expected, somewhat more de- veloped.

I have never seen any secondary roots sent off either into the interior of the wood, or between the bark and wood$.

I have met with a species flourishing on the Artocarpus integrifolia.

* I t will be interesting to compare this with grafts, on which subject I am quite ignorant. I think

i- I have seen seeds of Loranthus germinating on the succulent fronds of a Polypodium. $ Physiologie V&g&tale, vol. ii. p. 790 ; and vol. iii. p. 1411. 4 I have before mentioned that in one species of Viscum both primary and secondary external at-

tachments take place. A slight examination of another species, in which no lateral shoot had been developed, leads me to suspect that the mode of adhesion of Viscum album is not thoroughly under- stood ; and that the appearance of roots running between the bark and wood of the stock is, perhaps, attributable to a peculiar modification of the wood of the latter. Whatever the cause may be wit11

the attachment of Loranthus is not analogous to grafts.

the Ouzcla of Loranthus und Viscum. 51

The influence-these parasites possess over the stock is according to their reciprocal size : L. Scurrulu, generally attached to Melastoma rrzulubathricu, or other shrubs, frequently destroys them to a considerable extent. Others, again, which are minute in comparison with the stock, such, for instance, as those that grow upon trees, produce no appreciable deleterious effect.

The foregoing notes apply chiefly to the development of the ovula. I had

the generality of Loranthacee, with this species it is far different, the primary and secondary attach- ments taking place by suckers which appear to reach the older formed wood. From the first attach- ment roots are sent off upwards and downwards. These run to a considerable length, and adhere very firmly by means of suckers, which likewise are imbedded in the substance of the stem.

In this specimen the branches are confined to the stem originating from the primary attachment. The roots, however, have the power of sending off shoots. The suckers produce a most pernicious effect on the branches along which the roots take their course, and from their large size soon produce atrophy.

These roots have the same anatomy as the branches, the medullary rays being less distinct and the medulla almost obliterated ; it does exist, however, in a rudimentary state.

The suckers are composed of cellular tissue, and form part of the cortical system, with which they are continuous. The cells are long and arranged at right angles with the woody system. No cuticle covers the adhering surface of the sucker.

The pith is excentric, and, as might be expected, nearest the circumference on the side of the adhe- sion. The more vigorous and older of these suckers pierce the albumen to a greater or less distance ; but no identification of substance appears to take place, the fibres of the suckers being at right angles with those of the alburnum. In all probability they have not the power of piercing into the substance of the wood, their greater depth in the older and larger branches being owing to the deposit of new ligneous matter. At the same time a corresponding increase takes place in the sucker, which becomes hard towards its base.

TAB. IX. fig. 1. represents a sketch taken from a sucker about three inches below the axis ; irregu- lar fascicles of woody matter have passed off from the wood into the sucker, into which they penetrate deeply. They all appear to terminate at a short distance from the adhering surface of the sucker, which is entirely cellular, and much less coloured than the rest ; it is still large. The terminations of the woody fascicles are generally clavate. So great is this tendency to throw out suckers that when two roots encounter each other, as they frequently do, they throw out suckers and form mutual adhe- sions. In this case there is actual identification of structure, woody fibrous bundles passing off from both and becoming identified with the wood. See TAB. IX. fig. 4. I t does not take place through- out the whole length of the sucker, but is chiefly confined to its upper position.

There is in this no union between the woody systems, although the irregular woody bundles have at a, nearly reached the pith. The irregularities of this, observable at b, c, depend probably upon an attempt at formation of wood on this side. The depth at which the sucker has apparently pierced is owing in reality to its original attachment, which must have taken place when the stem of the stock was very thin : consequently the pith would be near the surface.

The upper bourrelet sufrounding the suckers is always the larger.

TAB. IX. fig. 2. represents the original attachment on the apex of a branch.

Still the edges of the wood of the stock are entire.

VOL. XVIII. M

82 Mr. GRIFFITH on the Development of

marked down several points for particular study at Mergui during the rainy season ; but it is now very probable that a considerable time will elapse before I can recur to this very interesting subject. A particular series of observa- tions is required as to the precise mode in which the radicle, or seminal sucker as it may be called, of the young parasite, as well as those of the lateral shoots, reach the surfwe of the wood. Observations on those species of Viscum which have a plurality of embryos, adhesion of this genus to t,he stock, will likewise ticulars.

E X P L A N A T I O N O F THE

TAB. IV.

and on the exact mode of afford many interesting par-

P L A T E S .

Fig. 1. Longitudinal section of an ovarium of Lorunthus Scurrula. a. Parietes of the calyx. b. Bases of two petals remaining. c,

Ovarium. d. Its upper portion, where it is continuous with the tissue of the style. e. Central, transverse, opake, linear spot, the site of the future excavation.

b. Commencement of the viscous tissue. c. Ovarium. d. Its upper portion, which is now traversed by a brown line passing through the centre of the style; the adjacent tissue being sphacelated. e. Extension of the sphacelated line trans- versely.

Fig. 2. a. Parietes of the calyx.

The excavation has just commenced.

In one instance the tissue of the sucker was prolonged downwards between the wood and bark of the stock.

To show the fact of a non-continuity of tissue, the section must always be carried through the centre of each sucker, and the branch to which it is applied. As these suckers have not a linear but a discoid attachment, a lateral section will give the appearance of an intermixture of fibres.

Fig. 2, 3 & 4. are taken from the same species. I have verified the above in one species belonging to the section Scurrula, from which the sketches were taken, and in one of the section Symphyanthus.

TAB. V I I I . fig. 5 & 6. represents a young plant of a species of Loranthus, attached by a broad base to an elevation of corresponding breadth of the branch, which, however, it overlaps : see fig. 7. The elevation visible in the branch is produced by the passage of the roots of the parasite under the bark. 'They expand so as $0 form what the French term a pdtt! d'oie. Here, again, the roots do not penetrate beyond the original attachment.

The centre of this prolongation was occupied by a ligneous fascicle.

the Ovula of Loranthus and Viscum. 83

Fig. 3. The same figures have the same references. The excavation has now increased, as is evident by the greater transparency of the tissue at e.

Fig. 4. The figures refer as before. The viscous tissue at b is now considerably developed, and of a fine green colour ; at d, the discoloured brown tissue of the apex of the ovarium, with the remains of the central brown line, is visible, and at e, a large excavation, occupied chiefly by dislocated cellular tissue.

The tissue at d, is, however, more blended with that of the calycine parietes, excepting its base, which is still brown. The parietes of the ovarium c, are reduced superiorly to a great thinness, owing to the development of the albumen at e. f. Is the incomplete embryo with its cellular funiculus.

a. Albuiiien. b. Cellular, lax funiculus. c, Embryo. d. Its cotyle- donary and unequal division.

Fig. 7. Ditto. More, and about half developed. b. Al- bumen. c. Embryo. d. Its radicular extremity, now inclosed almost entirely in the albumen. e. Sulcus along its lower portion, indicating the original division into two rather unequal cotyledons.

d, e. Have the same references. The coty- ledons are now adherent by their contiguous faces, although the sulcus is very evident. f. The basilar portion of the cotyledons where they do not become adherent. This subsequently forms one of the lateral slits.

b. The cotyledon ; the two being now entirely consolidated except at the basilar point.

There is generally some obliquity about the apices of the cotyle- dons.

Fig. 5 . a, b, c, d refer as before.

Fig. 6. A more advanced embryo detached, with the base of the albumen.

a. Fibrous ovarium.

Fig. 8. Same embryo detached.

Fig. 9. Nearly mature embryo. a. Its radicular end.

The cleft c exists on both sides.

TAB. V.

Fig. 1 . Mature fruit, separated from the integument of the calyx, and carrying with it the whole of the viscid matter, a, which is at this period transparent. b. Capsule inclosed within the viscid substance. c. Its

M 2

84 Mr. GRIFFITH on the Development of

stalk. d. Marks the termination of its angles, which are the only dense parts in its composition.

The angles are seen to terminate in little points, generally three to each. Their continua- tion down the stalk is likewise shown.

a. The viscous tissue which occupies the entire space between the outer part or cutis of the calyx and the ovarium, which is seen at b. c. The albumen. d. Radicular and partially exserted extremity of the em- bryo. e. Cotyledon cut through longitudinally. f, f. Situation of both lateral clefts. g. The plumula.

Fig. 2. The same, the viscid covering being removed.

Fig. 3. Longitudinal and central section of a mature fruit.

Fig. 4. Perfect embryo detached, both lateral clefts are shown.

Fig. 5 . Longitudinal and central section of ripe fruit of a Loranthus, species The ovariurn is in this species, in the ripe state at least,

The

Fig. 6. Base of the same ovarium or capsule, albumen and embryo separated At the base of the ovarium is a depression

Fig. 7. Embryo detached ; the brown apiculus is the remains of the original

The above figures refer to the same species as those of TAB. IV.

unknown. incomplete, its upper two thirds being dissolved into viscum. radicle is immense and almost entirely exserted.

from the viscous tissue. indicating its original connection with the pedicel.

lax cellular fiiniculus. One of the lateral clefts is visible. These three, 5 , 6, 7 . refer to the same species.

Fig. 8. Longitudinal section of an embryo of Loranthus, species unknown. c, c. Sites of the lateral a. Its radicular extremity.

clefts. d. Plumula. Fig. 9, 10, 11, 83; 12, refer to the same species. Fig. 9. Longitudinal section of the ovarium of a Loranthus, species unknown,

long before expansion. a. Calyx, tissue of. b. Ditto, mucilaginous white portion. c. Ovarium, now fibrous ; its communication with the base of the style is very distinct.

Fig. 10. Longitudinal section after the fall of the corolla and after impregna- tion. a, b, c. Have the same references as in fig.9. d. The more per- sistent base of the ovarium, which has undergone but little change.

6. Cotyledon.

the Ovula of Loranthus nnd Viscum. 85

e . Brownish rather indistinct line running towards the excavation, in which the now imperfect nucleus,f, of a cordate shape, is deve- loped.

Fig. 1 1 . Longitudinal section of a more advanced fruit ; the figures have the same references. The mucilaginous or now viscous tissue, 6, is much enlarged, and is deposited in cavities, which appear to be tole- rably distinct from each other; the two basilar ones, as in some others, are the largest. d. The diminished remains of the basilar part of the originally dense ovarium; it is the persistence of this portion that causes in part the production of the horns of the dbu- men. The line e is very distinct, and the tissue forming the mar- gins of the now large cavity much sphacelated. f. The albumen considerably altered in shape. g. The young em-

bryo attached very slightly to the part of the albumen correspond- ing to the termination of the line e.

The same phaenomena occur as in Loranthus Scurrulu.

Fig. 12. Embryo detached to show the large evascular funiculus.

Fig. 1 . Longitudinal section of an ovarium of a Loranthus, species unknown, a short time after the fall of the flower. a. Outer tissue of parietes of the calyx. b. Inner ditto commencing to become viscous. c. Ova- rium. d. Its base and denser portion, which produces the same effect on the albumen as above noticed. e. The line descending from the apex of the remains of the conical base of the style. f. Ovulum.

Fig. 2. Section not truly central. a, b. Refer as before. c. The fibrous walls of the ovarium. d. Its stalk, which is surrounded by viscous tissue.

The sphacelated apex of the remaining base of the style is evident. The communicating sphacelated line e has disappeared, the tissue continuous with the base of the style being truncate. e. The broad cellular attaching process of the albumen. f. The albumen : rudi- ments of two of its ascending cornua are visible. g. The embryo hanging down into a cavity formed in the albumen by excavation.

Fig. 3. Embryo detached. I ts funiculus is long, loosely cellular, and evascular,

Mr. GRIFFITH on the Developnzent of

far exceeding in bulk the embryo itself, in which the first trace of a cotyledonary division is visible.

n, b. The two divi- sions of the tissue of the calyx now nearly similar. c, c. The basilar portion of 6, which remains uncoloured and has a mucilaginous appearance. d. Remains of the stalk of the ovarium. e. Sphacelated communicating line, reaching to the apex of the radicle and tra- versing the original suspending processf, of the albumen g, of which two large ascending, and two minute descending cornua are visible. h, Embryo, with its radicle situated between the ascending cornua of the testa.

Fig. 5 . Capsule separated : the white lines represent its denser angles, from which processes are sent out into the albumen ; alternating with

-these are six furrows, along which the texture of the capsule, here very fine, dips into the albumen.

Fig. 6. The albumen and embryo removed from the integument ; the albumen is 6-cleft, the fissures at its apex being acute: between the cor’re- sponding basilar obtuse ones, ,and projecting beyond them, is the truncate subpeltate radicle.

Fig.4. Central and longitudinal section of a ripe fruit.

Fig. 7. Transverse section of albumen and cotyledons. Fig. 8. Embryo detached. Fig. 9. The same ; its cotyledons, which are always distinct, being separated.

The very small plumula is not visible. The whole of the figures of this plate refer to one species.

TAB. VII.

Fig. 1 , 2, & 3. Detached embryos of Loranthus Scurrula, showing the first changes that take place after the application of the ripe fruit to the bark of a tree.

Fig. 4. Embryo of the same more advanced in germination ; the commence- ment of the ‘‘ sucker” is now visible.

Fig. 5 . Fruit of Loranthus Scurrula cut through longitudinally, showing the first changes in situ.

tl2e Ouula (# Loranthus and Viscum. 87

Fig. 6. Germinating embryo of a Lormztl~us, species unknown, the a1haint.n remaining attached and inclosing the cotyledons.

The radicle of the parasite has not yet pierced the bark of the stock.

Fig. 7 . Ditto. Removed from its attachments and froni the embryo ; the half sphacelated cotyledons are somewhat separated.

Fig. 8. Albumen and cotyledonary end of the same embryo. Fig. 9. One of the cotyledons and plumula. Fig. 10. Germination of Loranthus rather advanced. The root has a t this

The rudiments of the second pair of period perforated the bark. leaves are visible.

TAB. VIII.

Fig. 1. Fruit and germinating embryo of Loranthus Scurrula cut through lon- gitudinally. The plumula is just exserted ; the radicle has not yet pierced the bark of the stock ; some of the viscuni is seen adhering to the fruit. N o change has yet taken place in the cotyledon. The radicle has become whitish in the centre ; the irregular shape of the sucker-like portion is visible, and appears to result from the siiiall opening in the parietes of the capsule.

The albumen has almost entirely disappeared, and the cotyledon is much shorter.

The root has pierced the bark, the contiguous portions of which are seen to be sphacelated ; and i b sucker-like extremity is seen to be expanded on the surface of the wood. The first pair of leaves have reached to a considerable size ; one, however, is cut away. This is viewed obliquely.

Fig. 3. More advanced state of a young plant of Loranthus Scurrula ? the upper portion of the stern being cut away.

This shows the great irregularity of the base of the axis of the parasite, the incomplete ring formed round its base in the ligneous system of the stock, and the lateral shoot.

Fig. 4. A similar young plant more advanced, perhaps of the same species : the sphacelated margins of the bark around the base of the parasite,

Fig. 2. Ditto, considerably more advanced.

and its partial destruction, with the course of the lateral shoot, are visible.

Fig. 5. Young plant of a Lormzthus attached to a stock. Fig. 6. Ditto. Longitudinal section of the conical base of its axis, togetlier

with that of the stock, the bark removed. Fig. 7. Portion of a lateral shoot of an adult Loranthus, with a cori-espotiding

portion of a stock, showing their mode of adhesion. Fig.8. Portion of the same cut through longitudinally, showing that the

sucker has pierced the bark and become applied on the surface of the wood of the stock.

TAB. IX. Fig. 1,2 & 3. Different sizes of parasites arid stocks cut through longitudi-

nally, showing that however varied the surface of the woody system of the stock may be to which the parasite is applied, there is no inut,ual communication between the two systems. I n other words, the woody systems of the stmock and parasite are contiguous, and not continuous.

Fig. 4. Longitudinal section of two lateral roots of Loranthus SCUITUZU, show- ing that these not only become occasionally attached by ‘‘ suckers,” but t,hat when this does take place, there is an actual, although par- tial, union between their woody systems.

EXPLANATION O F THE PLATES O F VISCUM.

TAB. X. Fig. 1 . Longitudinal section of an ovarium before the expansion of the flower.

b. The canal running from the centre of the stigma through the upper part of the ovarium, and termina- ting in the cavity d.

a. Parietes of the calyx.

c. Ovarium of the same structure with the calycine tissue. C, [(.

the Oouln of Loranthus cozd Viscuni. 89

Is the opake line of elongated tissue running through the centre of the ovarium, and terminating at the base of the nipple-shaped, cel- lular process e, which is central, and opposite to the termination of the canal b, nearly filling up the similarly shaped cavity d. 1 a. The nipple-shaped process from the same ovarium.

Fig. 2 . The same letters have the same references. The canal b is diminished i n diameter, hut increased in length. The tissue of the stigma, and that about the apex of the ovariutn is yellow. Taken from an ovarium before impregnation, but during expansion. 20. Nipple-shaped pro- cess of the same detached ; i t has become more conical.

Fig. 3 . Longitudinal section of ovarium after impregnation, that is, if the appearance of the stigma may be taken as a proof.

a. Calycine tissue ; the viscous tissue has begun to be developed. The line b is now closed, and of a light brown colour, and d is no longer visible, being entirely occupied by the process e : continuous with the line C a two curved brown lines are visible in e, the con- vexities of which look upwards.

(I have never observed more than two lines in this species). A lateral excavation is visible at f, the greater part of which is occu- pied by the body g, which hangs from the nipple at the termination of one of the curved lines.

The viscous tissue now occupies the chjef parts of the calycine parietes, and is internally in opposition with the now fibrous capsule, which is prolonged upwards into four or five horns, of which two only are visible in the section. The communication between the stigma and the cavity containing the nipple-shaped process e, is still traceable a t 6. The process e, with its two arclied lines, has undergone no change. The ovulum g, which, I should observe, is reduced to a nucleus, now fills completely the excavated cavity. In the axis of the upper half the embryo is visible in sitic : i t is rather excentric when compared with the axis of the nipple. The original cotyledonary division has disappeared, ex- cept towards its apex.

The letters have the same references. VOL. XVIII. N

,

Fig. 4. Longitudinal section of a nearly ripe fruit.

Fig. 5. Ovarium still more advanced.

90 MY. GRIFFITH on the Deueloprnent of

The lateral excavationf is much enlarged, as is likewise the young ovulum g . The line C a is pushed to one side.

5 a. Young ovulum detached from the same ovarium. Fig. 6. Ovulum a little more advanced, detached with the nipple-shaped pro-

cess, the brown ciirved lines of which were in this instance no longer visible ; the process is rather pczpillose at its apex.

The excavation has become much en- larged ; the ovulum g has now attained a considerable size, and has become nearly central. The commencement of its development up- wards into horn-shaped processes is visible at g a.

Fig. 7. Ovariurn still more advanced.

TAB. XI.

Fig. 1. Nipple-shaped process detached from an ovariurn soon after impregna- tion.

Its apex is of a light brown colour ; communicating with the lower parts of the curved lines is an obscure channel, the edges of which appear of a light brown. This appearance of a channel of commu- nication between the apex of the nipple-shaped process, to which, probably, the male influence is applied, did not appear to be uni- versal or even general. A vesicle filled with brown grumous gra- nules is seen attached to the lower part of one side of the process by a broad base.

The two curved lines are very conspicuous, and of a rather deep-brown colour. The apex appears papillose. The broad cellular, irregular portion visible on one side indicates the site of attachment of an ovulum.

Fig. 3. Ditto, with an ovulum more advanced, detached with the upper portion of the opake line or stalk. The young ovulum is now attached by a narrower base, and is evidently cellular.

Fig. 4. Ovulum at about the same period of development ; the attachment is very narrow : at the commencement of the narrow portion, and in its centre, a globular vesicle is just visible ; this is, I imagine, the

Fig. 2. Nipple-shaped process, with the central opake line dissected out.

the Ouula of Loranthus mid Viscum. 91

rudiments of the embryo. I must state, however, that this vesicle generally eluded observation.

Fig. 10. Ovulum arid nipple-shaped process detached ; on one side a lateral excavation is visible in the ovulum, in which the embryo (fig. 1 1 .) was lodged.

Fig. 11. Young embryo ; the apiculus is the part by which it is attached. Fig. 12. The same, highly magnified. Fig. 13. Embryo detached at a later period of its growth. Fig. 14. Ditto, showing the commencement of the division into cotyledons.

Fig. 6. Albumen detached, one of its (in this case four) cornua cut away longitudinally, to show the cavity in which the embryo is lodged.

Fig. 8. The same entire ; the apex of the radicle is just visible between the bases of the cornua.

Fig. 9. Mature embryo detached ; the slit and the incoriipletion of the adhe- sion of the rather unequal cotyledons are shown.

Fig. 5 . Transverse section of a fruit below the situation of the embryo ; in this case the ovarium has five rounded angles, each of which is pro- longed into a horn.

Fig. 7. Ditto, the division still more advanced. P