68 ELEMENTARY BIOLOGY. [CHAP. 



"b. The reproductive organs. 



These are to be found by examining the under surface of 

 the prothallus with | obj. 



1. The antheridia. Most numerous near and among the 

 rootlets. 



a. Their form: small hemispherical eminences. 



b. Their structure: made up of an outer layer of 

 cells containing a few chlorophyll-granules, and 

 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 

 antherozooids) resulting from its division: in the 

 latter cells, in ripe antheridia, spirally coiled 

 bodies (antherozooids) can be indistinctly seen. 



2. The antherozooids. 



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 antherozooid is often attached 

 a rounded mass containing colourless granules. 



b. Treat with iodine ; this stains them and stops 

 their movements, so that their form can be more 

 distinctly seen. 



3. The archegonia. Make vertical sections of the pro- 

 thallus passing through the cushion; either by simply 

 chopping down it with a razor, or holding it between 

 two pieces of carrot and cutting. Note in the 

 archegonia 



a. Their form: chimney-shaped eminences with a 

 small aperture at the apex. 



