THE FERN 137 



H. The antheridla, or male sexual organs. These are fre- 

 quently more easily studied on. smaller dwarf prothallia, 

 especially those which have been giowing crowded together, 

 and are consequently irregularly developed and devoted en- 

 tirely to the production of antheridia (not a strictly normal 

 condition). Examine under h.p. mature antheridia situated 

 near the edge of the prothallium, so that they may be seen 

 in side view. Note and illustrate in figures : 



1. The funnel-shaped basal cell. 



2. The ring cell surrounding the side of the antheridium. 



3. The disk-shaped cover cell. 



4. The central group of developing sperms, or sperm mother 

 cells. 



5. Mature antheridia, especially those borne on somewhat 

 dry prothallia, when mounted in water, will open and 

 discharge the sperms. Watch their escape and movements 

 and then stain with iodine. 



6. Observe the coiled, spiral body of the sperm, the numerous 

 cilia at the pointed end, and generally a vesicle, the remains 

 of the sperm mother cell, at the larger end. 



I. The archegonia, or feviale sexual organs. Mount a large, 

 heart-shaped prothallium with the lower side uppermost, 

 together with several dwarf prothallia, some of whose an- 

 theridia are likely to discharge sperms. Study the necks 

 of the archegonia projecting from the cushion back of the 

 notch. Note how they curve backward and downward from 

 the cushion. Some of the necks are likely to open. Observe 

 that sperms swimming freely in the water gather around 

 the open necks and enter them. Illustrate these features. 

 1. The structure of the arohegonium can best he studied from micro- 

 tome sections cut lengthwise of the prothallium (Sec. 212). The 

 base of the archegonium with the egg lies imbedded in the prothal- 

 lium. There are only tWo or three canal cells. 

 J. The young sporophytes. In cultures of prothallia two 

 or three months old, which have been watered from 



