A Method for Demonstrating the Shape of Meristematic Cells in PlantsAuthor(s): R. GaneSource: New Phytologist, Vol. 29, No. 1 (Mar. 29, 1930), pp. 77-79Published by: Wiley on behalf of the New Phytologist TrustStable URL: http://www.jstor.org/stable/2428348 .

Accessed: 18/06/2014 14:36

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.

.

Wiley and New Phytologist Trust are collaborating with JSTOR to digitize, preserve and extend access to NewPhytologist.

http://www.jstor.org

This content downloaded from 185.2.32.141 on Wed, 18 Jun 2014 14:36:21 PMAll use subject to JSTOR Terms and Conditions

t 77 1

A METHOD FOR DEMONSTRATING THE SHAPE OF MERISTEMATIC CELLS IN PLANTS

BY R. GANE

fRIESTLEY(1) has given his reasons for believing that cells in 1 apical meristems and in the cambium have plastic contents and a non-rigid wall, and considers that the shape of these cells is deter- mined by the pressure of surrounding cells.

The simplest representation of such a system appears to be that of a compact mass of approximately uniform soap bubbles. Such a system has been considered at length by D'Arcy Thompson in his book Growth and Form. This method does not lend itself as a con- venient demonstration for class use, and the following method was devised to meet the teaching needs in the Botany Department at Leeds University.

Spheres of about i cm. diameter, made from well-handled plasti- cine, are dusted with powdered talc (French chalk), by rolling them in a dish well dusted with the talc. A cylindrical container, such as the metal cup of a thermos flask, is well dusted inside with the talc, the pellets put in and gently shaken down. A glass stopper, which will slide easily in the cup, is also dusted with the talc and then rammed down into the cup. The pellets are deformed by the pressure and are packed tightly together. After this treatment the pellets may be separated very easily from one another and are found to be irregular plane-sided solids having from twelve to fourteen faces, and are very similar in form to the macerated meristematic cells of Vica Faba examined by Tupper-Carey and Priestley(3). If a per- manent copy is required, this may be obtained in plaster of Paris by pouring a little thin plaster into the cup after the first layer of solids has been removed; or alternatively, by using putty instead of plasticine.

By regulation of the amount of chalk used, one can cause the pellets to adhere together fairly well but not to the cup, so that they may be removed from the cup as a mass. Using a knife dusted with chalk, and exercising a little care, the mass may be cut in any direc- tion without disturbing the packing. Such sections are not unlike those made longitudinally through part of the apical meristem of the higher plants.

This content downloaded from 185.2.32.141 on Wed, 18 Jun 2014 14:36:21 PMAll use subject to JSTOR Terms and Conditions

78 R. GANE

It is obvious that the method described above will not give regular solids, since it does not involve a systematic packing of the spheres prior to deformation. Using a rectangular container, the spheres were packed regularly in three different ways and then subjected to pres- sure. It is interesting, in that the case where "closest packing" is used, that is where one sphere is surrounded by and touches twelve others, a solid figure is obtained not with twelve faces but with fourteen, reminiscent of the well-known tetrakaidecahedron of Kelvin (2).

Another modification of this method is to pack the pellets to a thickness of three layers on a strong glass or metal plate, then cover with another plate of the same breadth, and after clamping iron strips to two opposite edges of the plates apply pressure perpen- dicularly to the surface of the plates. In this way one can compress the solids in one direction and cause them to elongate in another at right angles to the applied pressure. The appearance obtained is not unlike a surface view of the cambium of dicotyledons.

The plasticine is most easily recovered for use by shaking the solids from the experiment in a bottle of warm soapy water for a short time, rinsing with clean water, and then drying on a cloth in a warm place; most of the French chalk is removed so that the plasticine can be moulded into large masses.

A closer analogy to the conditions in a plant meristem would be obtained by using spheres of material that could be made to swell. Dry peas packed in a bottle and then soaked with water have been used, but with little success. A suggestion that pellets of dough be packed in a box and allowed to rise and then baked has been tried. The difficulty is to control the amount of swelling due to the yeast and early part of the subsequent baking.

SUMMARY

A method is described whereby spheres of plasticine may be pressed together and then taken apart so that changes in shape can be examined.

The effect of pressing spheres in various packings was tried. The most interesting case is that where closest packing gives solids resembling tetrakaidecahedra.

The writer is indebted to Professor J. H. Priestley for suggest- ing the problem and for his helpful criticism, and to the other members of the Botany Department for communicating their experiences with this problem.

This content downloaded from 185.2.32.141 on Wed, 18 Jun 2014 14:36:21 PMAll use subject to JSTOR Terms and Conditions

Review-Plant Biology 79

REFERENCES

(I) PRIESTLEY, J. H. The meristematic tissues of the plant. Biological Reviews, 3, I. 1928.

(2) THOMSON, Sir W. On the division of space with minimum partitional area. Phil. Mag. (5), 24, 503. I887.

(3) TUPPER-CAREY, R. M. and PRIESTLEY, J. H. The cell wall in the radicle of Vicia Faba and the shape of meristematic cells. New Phytol. 23, I36. 1924.

REVIEW

Plant Biology. An outline of the principles underlying plant activity and structure. By H. GODWIN, M.A., Ph.D. Cambridge Univer- sity Press, I930. Pp. ix + 265, with 67 figures in the text. Price 8s. 6d.

This book has been specially written to provide collateral reading to a course for first-year medical students in the University of Cambridge. It departs widely from the traditional text book of elementary botany, partly, though not wholly, on account of the reader to whom it is addressed, and the severe compression which has been necessary. It stresses the physiological and biochemical points of view, at the expense of the wealth of structural detail so beloved a decade ago. In this it is symptomatic of present-day tendencies, and as a reed to indicate the direction of the modern breeze it could hardly be bettered. If it leans a little heavily with the wind, that is of comparatively small account.

The impression left by a first reading of the text is one of surprise at the immense amount of information that has been packed within less than three hundred pages, intended as the printed companion to not much more than a dozen lectures. To get into these narrow limits an informative account of the life of plants and its "physico-chemical background," has naturally involved the omission of much that would ordinarily be expected under the heading of "Plant Biology," and opinions will inevitably differ as to the wisdom of the omissions. The most notable of the author's sacrifices are the reproduction of flowering plants, and any serious treatment of " alternation of generations" in lower groups. Cambia and secondary thickening, except in Fucus, are also passed over. The plant types selected for description have necessarily been few, but they are judiciously chosen and skilfully described to exhibit general principles such as the development of sex and soma, the differentiation of tissues and organs, and division of labour. It seems a little unfortunate, how- ever, that speculative matter concerning phyletic origins has been allowed to enter into the description of so limited a range of types. Its influence upon elementary students is surely likely to be in the direction of loose rather than of exact thinking.

It is to be feared that the book will prove stiff reading to the average first- year student, and will, for the same reason, prove unsuitable for use in schools. A considerable knowledge of chemistry and physics is assumed, and when one finds the author describing (pp. I7 et seq.) the magnitude of colloidal particles, with hints concerning the methods of measuring them, one rather wonders what he would have advanced classes learn. It is probably impossible to explain

This content downloaded from 185.2.32.141 on Wed, 18 Jun 2014 14:36:21 PMAll use subject to JSTOR Terms and Conditions