PLANT LIFE IN PONDS & STREAMS 



in size. At intervals there are larger cells and as the 

 plant increases in length they are emptied periodic- 

 ally, so they are evidently used as food stores. From 

 time to time portions of the plant break away, worm 

 their way out of the jelly and move about, rather 

 after the manner of a worm. Eventually, these 

 wanderers come to rest and become surrounded with 

 more of the blue-green jelly, thus forming a new 

 Nostoc colony. 



These plants sometimes appear, apparently from 

 nowhere, on garden paths, walls and similar situa- 

 tions, during damp autumn weather. On this ac- 

 count the plants have been called "fallen stars." 

 Their appearance is not so mysterious as it might 

 seem for the Nostoc colony has probably been where 

 it is found, all through the summer, in a dried up, 

 contracted state. Only when rain comes, does the 

 jelly envelope absorb water, swell up and assume 

 its normal appearance. The blue-green scum which 

 floats on stagnant water is a closely related plant. 



Another plant which looks like scum on the water 

 is known as Spirogyra and a very beautiful object 

 it makes for the microscope. It is bright green, 

 without a bluish tinge, so it need not be confused 

 with the plant we have just mentioned. There are 

 seventy or so different kinds of Spirogyra, therefore 

 our description must be the one that will apply 

 to all. The plant is thread-like and, even in 

 the larger kinds, the threads are not more 

 than one-hundredth part of an inch in diameter. 

 Like Oscillatoria the plants are not attached 



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