A MANUAL OV BOTANY 97 



constitutes the individual ])laiit ? What observations have 

 you made that form this couelusion? 



Typp: 4. Hydkodictiox (Water Nkt) 



Habitat. This alga is found in comi)aratively stagnant 

 water, and appears at first glance much like the filamentous 

 algai to be investigated later {dadoplun-a, vancheria), but 

 study shows it to be far different. It may be grown with 

 considerable success in aquaria. 



Structure. Examine (/y>) and m. Observe the very peculiar 

 attachment of the cells to each other. What is formed by 

 this attachment? AVhat appropriateness has the term 

 loater net? What is the distribution of the chlorophyll? 

 Compare (in this particular) with the vaucheria. What do 

 you find regarding the size of the nets ? Are all alike in 

 size and shape of the " meshes " ? 



Reproduction. Examine a cell of the largest size with a 

 microscope of comparatively high power. Possibly you 

 may find the contents assuming a netlike appearance. 

 This indeed happens ; the old cell wall breaks down, and the 

 tiny net escapes as a glove-fingerlike structure. This is 

 the common method of reproduction. How will this ex- 

 plain, in part, the varying size of the nets ? While examin- 

 ing the large cell look for oil globules. 



Drawing. Make drawings showing nets of various sizes; 

 also a single cell, the largest you are able to find. 



Explanatory note. Water net is a remarkable relative of 

 pleurococcu.s, each large cell producing myriads of exceed- 

 ingly small zoospores which never escape from the large 

 mother cell, but finally arrange themselves in such relation- 

 ship to each other that when they begin to grow, tiny nets 

 are the result. Such a close connection of cells, otherwise 

 independent, is called a colony. 



What advantage can there be in such an arrangement? 



