TYPES OF CRYPTOGAMS ; THALLOPHYTES 249 
the surface of the enveloping cells which enclose the spore. What 
is their number and form? What is their relation to the cells form- 
ing the crown? Focus so as to see the large egg-cell (odsphere or 
odspore) which constitutes the center of the fruit. Can you determine 
anything regarding its contents? 
Search for young odgonia and if practicable describe and draw 
them in several stages of development. Their structure can be seen 
much more easily than that of the 
antheridia. Make drawings to illus- 
trate various details of structure. 
290. Characee. Nitella 
and Chara are the genera 
composing the group Chara- 
cee, a group of green alge 
differing widely from any 
others. They show in a won- 
derful manner simplicity of 
cell-structure with a high 
> 1 i Fic. 182. — Part of a Leaf of Fig. 181. 
egree oO organization. 
(Considerably magnified.) 
Scarcely less wonderful are a,antheridium ; 0,odgonium. At the 
the care and precision with _ Tight are a young antheridium and 
which botanists have worked 
out their life history. Asastudy in evolution the Characee 
may be considered as representing the highest develop- 
ment attained along the line of filamentous green alge, 
which, while preserving their algal characteristics, are 
comparable in a remarkable degree with moss- and fern- 
plants and with seed-plants. Every cell in the plant has 
been accounted for and is understood in regard to origin, 
relationship, and function. With harmony of structure 
throughout, it has organs comparable to root, stem, and 
leaf in seed-plants, each with characteristic structure and 
