110 MORPHOLOGY AND LIFE HISTORY 



ful observation, observe a spore escaping from the 

 opening in the tip of the sporangium. If so, give 

 careful attention to the mode of locomotion of the 

 spore, and describe how its locomotion is accom- 

 plished. Since it has motion (as animals do) it is 

 called a zoospore. The zoospore soon comes to 

 rest. 



3. If the material contains germinating zoospores, 

 carefully describe them. 



4. Make drawings illustrating all you have observed 

 under F. 



G. Sexual Reproduction: 



1. In " fruiting" material, observe the lateral organs 

 that bear the gametes. These are the reproductive 

 organs. As is seen, they are of two kinds. 



2 . The larger, oval-shaped organ is called the oogonium. 

 Is the oogonium cut off from the parent filament 

 by a wall? On one side observe the rostrum, or 

 beak, through which is an opening or pore. In 

 material at a suitable stage may be observed a 

 portion of the contents of the oogonium being 

 voided or discarded. The protoplasm that re- 

 mains in the oogonium now becomes organized into 



the larger gamete, or egg (oosphere). Is its wall 

 composed of cells, or is it a unicellular organ? 



3. By the side of the oogonium 1 find a slender branch, 

 usually recurved at the end. Is this branch cut off 

 from the parent filament by a wall? Is the tip 

 cut off from the rest of the branch? This tip bears 

 small gametes, that swim about by means of two lash- 

 like cilia. They are the spermatozoids, or sperms. 



J If the species is V. geminata, instead of V. sessilis, the reproductive 

 organs will be found on the same lateral branch. The above directions 

 will not apply in detail to any species except V. sessilis. 



