XI 11 EQUISETINE^ 429 



spicuously granular, and forms the large vesicle attached to tlie 

 posterior coils of the free spermatozoid. The mucilaginous 

 change in the walls of the sperm cells begins about the same 

 time as the differentiation of the spermatozoids. 



The free spermatozoids consist of from two to three complete 

 coils, of which the forward one or two are very much smaller 

 than the very large and broad hinder one, which encloses the 

 vesicle. The cilia are much like those of the Fern spermatozoid, 

 but somewhat shorter. The cover cells of the ripe antheridium 

 are forced apart by the swelling of the mucilage from the dis- 

 organised walls of the sperm cells, which are forced out of the 

 opening into the water, where the remaining wall of the sperm 

 cell is dissolved and the spermatozoid set free. When in 

 motion a peculiar undulation of the large posterior coil is 

 conspicuous, a phenomenon which has also been observed in the 

 quite similar spermatozoids of Osmunda. 



The Archegonium 



The young female prothallium is always a cylindrical mass 

 of cells with a series of thin lateral lobes. After the archegonia 

 begin to form and a definite apical meristem is established, the 

 formation of these lobes is almost exactly like the similar ones 

 in young plants of Anthoceros fusifonnis. The exact relation 

 of the growing point in the older prothallium to the primary 

 one could not be made out. In the former this arises, according 

 to Buchtien,^ upon the under side of the prothallium, without 

 any apparent relation to the primary growing point. This 

 much is certain, that just before the first archegonium appears, 

 there is formed a cushion not unlike that of the Ferns. In the 

 youngest condition this in profile (Fig. 223, A) shows an 

 evident apical cell (probably one of several), not unlike that of 

 the Ferns ; but the great difficulty of obtaining accurate sections 

 through it made it impossible to follow exactly its further 

 development. This much can be stated confidently, however, 

 that at the time when the first archegonia are produced, the 

 structure of the prothallium is essentially that of Osiimnda or 

 Marattia, and consists of a central massive midrib and a one- 

 celled lamina, which is not continuous, but composed of 

 separate lobes. A similar condition exists in Osmunda, where 



1 Buchtien (i). 



