204 



ELEMENTS OF STRUCTURAL I'.oTAXY. 



Fig. 254. 



aquatics by the whorls of so-called 

 leaves which encircle the stem, 

 also by the general gritty naturcj of 

 the plant. A very offensive odour 

 is emitted by the plant in the co 

 of decay. Its green colour shows at 

 once the presence of chlorophyll. On 

 the branches you may observe num- 

 bers of minute, more or less rounded, 

 bodies; Fig. 255 is an enlarged view 

 of one of them. Here, at &, is shown 

 a large central nucleus (the nucule) 

 enclosed in a spiral covering. This 

 spiral consists of five long cells side 

 by side, all of which wind about the 

 central body, and have their ends 

 projecting above it. The nucule is a 

 row of cells of which the highest is 

 the germ-cell, and the whole answers, 

 in fact, to the archegonium of the 

 Bryophytes and Pteridophytes. It 

 is, in this plant, called the carpo- 

 gonium. Just below it is a globular 

 body made up of eight triangular 

 shield - shaped segments arranged 

 about a central cavity. From the 

 inner end of each segment several 

 coiled filaments of many cells each 

 project into the cavity. At maturity 

 the shields separate, and the, fila- 

 ments eventually break up into their 



Fig. 2o4.Chara/rayilus; natural size. (Thom&) 



