PLANT LIFE IN PONDS & STREAMS 



to any support. Each thread is composed of 

 many cells, arranged end to end; we can dis- 

 tinguish the cell walls clearly, but what will chiefly 

 attract our attention are the beautiful bands of 

 green colouring matter, running spirally, round each 

 cell. If we are fortunate, we shall see the plant in 

 the act of increasing; this is not the simple opera- 

 tion we witnessed in the silk weeds. From two 

 threads lying parallel to one another, we shall see 

 swellings arise on the adjacent cell walls ; the beauti- 

 ful spiral bands will begin to break up at the same 

 time and to collect in a mass towards the centre of 

 each cell. The swellings of adjacent cells touch, 

 their end walls, break down so that the two cells 

 become connected, our figure shows the fusion taking 

 place, then the contents of one cell passes into the 

 adjacent cell and fuses with the contents of the 

 latter. The new cell, which now contains not only 

 its original contents but that from a cell in another 

 plant, becomes detached from the thread, assumes 

 an oval shape and sinks to the bottom of the pond, 

 where it rests awhile. At a later period the cell 

 wall bursts and a new thread of Spirogyra develops 

 from it. 



When we are examining Spirogyra we may notice 

 some very minute brick-red, spherical bodies adher- 

 ing to the green threads. These are little pond 

 animals, known by the name of Vampyrella Spiro- 

 gyrse. This little creature passes through an inter- 

 esting and easily observed series of changes. Its 

 life is very uneventful, consisting of a good meal of 



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