248 



GENERAL MORPHOLOGY OF PLANTS 



branches are formed, which are separated from the parent wall 

 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 fertiliz- 



Fig. 198. 



Fertilization of Vaucheria. fn, female nucleus; mn, male nucleus. The different figures 

 show various stages in the fusion of the nuclei. (After Oltmanns.) 



ation 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^). 



382. General characters. The stoneworts or bass weeds 

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

 organization, representing the highest development of the green 

 algae, and only the most general characters will be given here. The 

 plants vary from a few centimeters (an inch or so) to more 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 naked species of Char a 

 (most species of Chara have a cortex of cells covering the 

 internodal cells), consist of a single long cylindrical cell, usually 

 several centimeters long, but in Nitella sometimes 30 centimeters 

 (i foot) long. At the nodes are whorls of short cylindrical out- 

 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 Chara are 

 covered with a cortex of cells. The sexual organs are sperm and 



