458 ELEMENTARY BIOLOGY. [ClIAP. 



p. The root-hairs : each composed of a single 

 cell which contains no chlorophyll. 



c. The atitheridia and archegonia : the former can 

 just be seen with an inch objective as minute 

 eminences on the under surfoce of the older 

 parts of the prothallus especially among the 

 root-hairs; the latter are partly imbedded in 

 the cushion. 



b. The reproductive organs. 



These are to be found by examining the under surface of 

 the prothallus with ^ obj. 



1. The ajithcridia. Most numerous near and among the 

 root-hairs. 



a. Their form : small hemispherical eminences. 



b. Their structure: made up of an outer layer 

 of cells containing a few chlorophyll-granules, 

 through which can be seen, according to the 

 stage of development, either a single central cell, 

 or a number of smaller cells {mother-cells of 

 spcrmatozoids) resulting from its division : in the 

 latter cells, in ripe antheridia, spirally coiled 

 bodies (^<permatozoids) can be indistinctly seen. 



2. The spcrmatozoids. 



Some of these are sure to be found swimming about 

 in the water if a number of ripe prothalli are examined. 



a. Small bodies, coiled like a corkscrew, thick at 

 one end, and tapering towards the other, which 

 has a number of cilia attached to it. To the 

 thicker end of the spermatozoid is often attached 

 a rounded mass containing colourless granules. 



