PLANT LIFE IN PONDS & STREAMS 



easy to describe nor, so far as we know, has it ever 

 been explained. A thread will be seen to glide back- 

 wards and forwards, becoming somewhat curved 

 and, at the same time, revolving on its axis. Eel- 

 like is perhaps a good description of the movement. 

 It is possible to distinguish this plant from other 

 pond dwellers by its slimy *' feel " which arises from 

 the fact that each thread is enclosed in a jelly-like 

 sheath. 



The silk weeds, Cladophora Glomerata are some- 

 what similar in apperance to the plant we have just 

 described, but they are denizens of running streams 

 rather than of ponds. They are the green thread- 

 like plants we so often see attached by one end to 

 rocks and stones beneath running water. Each 

 plant consists of a long, cylindrical structure com- 

 posed of several cells. We mention the silk weeds 

 here, because they are best of all plants for showing 

 cell growth. This growth takes place at or near the 

 unattached end of the plant and is easily observed. 

 The end cell may be watched for the process. Its 

 green contents will be observed to contract in the 

 middle so that it assumes an hour-glass shape. 

 Then, where the contraction has taken place, we 

 can watch the formation of a wall right across the 

 cell, so that when the process is completed we have 

 two cells where formerly there was one. More 

 rarely, the contents of a cell will be observed to 

 bulge out a side wall, then a new wall is formed to 

 divide it off from the main cell and thus the begin- 

 ning of a branch is formed. The silk weeds exhibit 



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