PTERIS AQUILINA. 113 



On rather young gametophytes antheridia may often 

 be seen extending outward from almost any of the 

 marginal cells; on old gametophytes they do not grow 

 in this position, but on a definite part of the under sur- 

 face of the body. They may be most easily studied on 

 young gametophytes. Locate good antheridia in such 

 position as to be seen from a side view. Study, 

 observing: 

 i. The short antheridial stalk, and how it arises from 



the body. 



ii. The wall cells; note that the tip cell is arranged so 

 as to make a ready opening for the escape of sperms 

 when ripe. 



iii. The centrally placed sperms or sperm mother-cells, 

 iv. Draw. 



By mounting in water some rather dry gametophytes 

 that are producing antheridia, it will often be possible 

 to obtain sperms in the process of escaping. Make 

 such a mount, and observe: 

 v. The form and movement of the sperms. Stain with 



iodin, and observe: 

 vi. The cilia. 



vii. The body of the sperm, 

 viii. Draw. 

 b. Archegonia. 



Mount fully formed gametophytes with the ventral 

 surface uppermost, and observe: 



i. The archegonial necks protruding from the surface, 

 and curved away from the notch. Sometimes the 

 opening into the neck can be seen. Draw. By 

 means of microtome sections cut perpendicular to 

 the surface and along the longitudinal axis of the 

 gametophyte, study the structure of the archegonium, 

 observing: 



