228 GENERAL MORPHOLOGY OF PLANTS 



by cross walls. Some of these become broadly oval and form 

 the egg cases (oogonia), each with a single egg. Others are 

 slender and more or less curved. These are the sperm cases 

 (antheridia), and contain numerous biciliate sperms. In fertili- 

 zation a sperm enters the egg case at the opened end, passes into 

 the egg and unites with one nucleus at the center. A thick-walled 

 resting spore is now formed, the oospore, which in turn germinates 

 and produces the green-felt plant again. 



STONEWORTS, OR BASS WEEDS (CHAROPHYCE^E). 



369. General characters. The stoneworts or bass weeds 

 occur in fresh or brackish water. They have a very complex organ- 

 ization, representing the highest development of the green algae, 

 and only the most general characters will be given Jjp^e. The 

 plants vary from a few centimeters (an inch or so) to m&Fe than a 

 meter (several feet) long, and are usually much branched. The 

 stems are slender and made up of distinct nodes and internodes. 

 The internodes in Nitella, and in the decorticated species of 

 Cham, consist of a single long cylindrical cell, usually several 



centimeters long, but in 

 Nitella sometimes 30 cen- 

 timeters (i foot) long. At 

 the nodes are whorls of 

 Fig. i 9 o. short cylindrical out- 



Cyciosis in Nitella. growths resembling 



branches. They are called " leaves " but are not true leaves. 

 The true branches arise in the axils of these " leaf " whorls. 

 The internodes in most species of Cham are covered with a 

 cortex of cells. The sexual organs are sperm and egg cases 

 (antheridia and oogonia). The stoneworts are remarkable for 

 the striking movement of the protoplasm in the cells. The proto- 

 plasm flows down one side of the cell and back on the other, turn- 

 ing at the ends. 



