12 GENERAL BIOLOGY. 



m 



(c) Mode of debiscence (look for one that has 



opened). 

 3. Spores. Examine with high power. Note : 



(a) Size. (Measure.) 



(b) Form. 



B. SEXUAL GENERATION. Prothallium. 

 I. Examine a prothallium with the naked eye or a 

 hand-lens, then mount in water, and examine 

 with the lowest power. 

 Sketch. Turn it over and sketch again. 

 II. Reproductive organs. 



1. Examine the lower surface of the prothallium 

 with the high power. Note : 



(a) Archegonium : a chimney-like structure, 



brownish in late stages. In the cavity 

 at the bottom lies the oosphere. /Sketch. 



(b) Antheridium : a rounded projection with 



an outer layer of cells containing a few 

 chlorophyll-grains. In different stages 

 of development there can be seen in 

 the centre either a single cell or a num- 

 ber of smaller cells (mother-cells of 

 spermatozoids) produced by the divi- 

 sion of the central cell. The mother- 

 cells in ripe antheridia contain spirally 

 coiled bodies (spermatozoids). /Sketch. 



