92 TYPE STUDIES 



B. Study fruiting material under h.p. Draw : 



1. The female organ, or oogonium, which is a large swollen 

 cell that develops a single female gamete, the oosphere, 

 or egg. Note the rounding off of the Qg% before fertiliza- 

 tion as a naked protoplast, and the formation of a pore or 

 cleft to allow the entrance of the sperm. 



2. The oospore within the oogonium developed from the 

 fertilized egg, which forms a heavy wall about itself. 

 Observe the changed appearance of the cell contents, due 

 to the presence of much food material. Test for starch. 



3. The male organs, or antheridia, groups of small disk- 

 shaped, almost colorless cells, each of which develops two 

 sperms. The sperms have a circle of cilia at one end. 



Because the form or morphology of these gametes (eggs and 

 sperms) is unlike, this type of sexual reproduction is called 

 heterogamy (meaning unlike gametes). 



C. The large zoospores may be present in living material. 

 These are formed singly in the cells. Note their slow swim- 

 ming and the circle of cilia at one end. 



Should the material of CEdogonium be of a species with the 

 peculiar dwarf male plants, the laboratory directions would have 

 to be considerably changed. 



Reference (on the formation of the caps). Goebel, 16, p. 44. 



Questions. What advances does (Edogonium show over Ulo- 

 thrix (1) in the structure of the vegetative cells, holdfasts, 

 and tip of filaments ? (2) in the sexual organs and gametes ? 

 Would the oospore from its structure be expected to ger- 

 minate at once, or is it fitted to carry the plant over unfavor- 

 able seasons ? Describe the life history of (Edogonium. 



86. Coleochaete (App. 12). If living material is available, study its expanded 

 growth over the substratum, as illustrated by some of the commonest species. 

 Preparations stained in hematoxylin (Sec. 212) and mounted entire in bal- 

 sam are excellent for detailed examination. 



A. Under l.p. note the radiate arrangement of the cells from a center of 

 growth. Is the disk one layer of cells thick or more ? Where does cell 



