TYPES OF CRYPTOGAMS; THAXLOPHYTES 



249 



the suiface of the enveloping cells \fhich 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 (oosphere or 

 oospore) which constitutes the center of the fruit. Can you determine 

 anything regarding its contents ? 



Search for young oogonia 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 structm-e. 



290. Characeae. — Nitella 

 and Chara are the genera 

 composing the group Oharor 

 cece, a group of green algge 

 differing widely from any 

 others. They show in a won- 

 derful manner simplicity of 

 cell-structure with a high 

 degree of organization. 

 Scarcely less wonderful are 

 the care and precision with 

 which botanists have worked 

 out their life history. As a study in evolution the CTiaraoece 

 may be considered as representing the highest develop- 

 ment attained along the line of filamentous green algae, 

 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 



Fig. 182. —Part of a Leaf of Fig. 181. 



(Considerably magnified.) 

 a^antiieridium; o,oc>gonium. At the 



right are a young antheridium and 



archegonium. 



