1.0 INTRODUCTION

There are about 20,000 species of Bryophytes, plants that lack vascular tissue.

They are found throughout the world. Although more prevalent in moist and shady

areas, Bryophytes can be found in alpine and artic regions, where they are subjected

to freezing, and some in deserts, where they are desiccated most of the time. One of

the most abundant Bryophytes, Sphagnum, is found in bogs worldwide, and forms

peat, a source of fuel when compacted, and a soil texturizer when less "decomposed".

Associations of Bryophytes with mycorrhizae are common. The three phyla of

Bryophytes are distinguished from each other on variations of sporophyte structure

and gametophyte morphology. All Bryophytes have a predominant gametophyte

generation.

Bryophytes also need a moist environment to reproduce. Their flagellated

sperm must swim through water to reach the egg. So mosses and liverworts are

restricted to moist habitats. There are no mosses in the desert. But mosses are

surprisingly resistant to drying up, and can survive under very harsh conditions.

Mosses are the most abundant plants in both the Arctic and the Antarctic. Asexual

reproduction in bryophytes is accomplished by fragmentation or by tiny vegetative

"sprouts" called gemmae, which form in special little structures called gemmae cups.

There are 3 objectives on this experiment which are to describe the plant life

cycle and the concept of the dominant generation. Secondly, to describe the life

histories and related reproductive structures and to distinguish features of the seedless

non vascular plant.

2.0 MATERIALS

2.1 Living mosses (Polyticum sp.)

2.2 Compound microscope

2.3 Dissecting microscope

2.4 Slide and coverslip

2.5 Distilled water

3.0 PROCEDURE

3.1 Male and female gametophytes identified. Sporophytic and

gametophytic generation of the moss differentiated.

3.2 Moss of female gametophytes examined. Paraphyses, archegonium,

neck canal, neck, egg, venter and stalk identified.

3.3 Sperm producing of the male gametophytes examined. Paraphyses,

anteridium, spermatogenous tissue, and stalk identified.

3.4 Mature sporophyte attached to the erect parent gametophyte. Calyptra,

operculum,peristome and spore identified.

4.0 RESULTS

Figure 4.1 Figure 4.2

40 X magnification of Polyticum sp.

Under dissecting microscope

40 X magnification of Polyticum sp.

Under compound microscope

5.0 DISCUSSION

6.0 POST-LAB QUESTION

6.1 What function do you think the root-like rhizoids at the base of the

plant perform?

The function of rhizoids is to be the root system for bryophytes —

plants without vascular tissue, such as mosses and liverworts. Like a

tangled mass of silken white hair, the rhizoids can tie a plant to its

substrate, whether it be soil, solid rock, or other material in which it

grows. Likewise, the greatly increased surface area of many strands of

hair efficiently soaks up water and dissolved   minerals .

6.2 Explain why water must be present for the bryophytes to complete the

sexual portion of their life cycle.

The male sex cells,androcytes of bryophytes are motile and require a

medium to swim in to reach the female sex organ for fertilisation.

Hence water is essential as it becomes the medium for the androcyte to

swim.

6.3 Describe the difference between a sporophyte and gametophyte.

Sporophyte:

1. It is an independent plant with diploid chromosome number.

2. In algae, the sporophyte is confined to zygote. In bryophytes, the

sporophytes are a complex structure but is dependent on gametophyte.

3. In pteridophytes, gymnosperms and angiosperms the sporophyte is

dominat.

4. In lower groups of plants, sporophyte reproduces by spores spores

that give rise to gametophyte.

5. In higher plants sporophyte performs vegetative and sexual

reproduction.

Gametophyte:

1. It is an independent plant with haploid chromosome number.

2. In alga those and bryophytes the gametophyte is dominant.

3. In pteridophytes, gymnosperms and angiosperms, the gametophytes

are very much reduced.

4. In lower group of plants, gametophyte reproduces vegetatively,

asexually and sexually. Vegetative and asexual reproduction produces

gametophytes whereas sexual reproduction produces zygote, which

represents the sporophyte.

5. In higher plants, the gametophyte represents the gametes only

which fuse to form sporophyte.

7.0 CONCLUSION

8.0 REFERENCES

9.0 APPENDICES

Figure 8.1 Figure 8.2

40 X magnification of Polyticum sp. Under dissecting microscope

40 X magnification of Polyticum sp. Under compound microscope