FERNS. 



181 



These are the an- 



tered over this portion of the prothallium 

 theridia. If the pro- 

 thallia have not been 

 watered for a day or 

 so, we may have an 

 opportunity of see- 

 ing the spermato- 

 zoids coming out of 

 the antheridium, for 

 when the prothallia _ .. ., ... , ls '. 223 ' ,, 



r Section or anthendia showing sperm cells, and spermato- 



are freshly placed in zoids in the one at the ri s ht - 



water the cells of the antheridium ab- 

 sorb water. This presses on the con- 

 tents of the antheridium and bursts the 

 cap cell if the antheridium is ripe, and 

 all the spermatozoids are shot out. 

 We can see here that each one is 

 shaped like a screw, with the coils at 



Fig. 224. ^ ' 



Different views of spermatozoids; first close. But as the spermatozoid 



42, 43, in a quiet condition; 44, in , . ,, . ., 



motion (Adiantum concinnum). begins to move this coil opens some- 



what and by the vibration of 



the long cilia which are on the 



smaller end it whirls away. In 



such preparations one may often 



see them spinning around for a 



long while, and it is only when 



they gradually come to rest 



that one can make out their 



form. 



373. Archegonia. — If we now 

 examine closely on the thicker 

 part of the under surface of the 

 prothallium, just back of the 

 " sinus, 



Fig. 225. 



Archegonium of fern. Large cell in the 

 We may See longer venter is the egg, next is the ventral canal 

 cell, and in the canal of the neck are two 

 StOUt projections from the Surface nuclei of the canal cell. 



of the prothallium. These are shown in fig. 314. They are 



