106 



MICROSCOPY FOR BEGINNERS. 



Fig. 85. Spirogyra. 



4. SPIROGYKA (Figs. 85, 86). 



The SpirogyrcB are easily recognized by the beautiful 

 spiral bands of green within each cell, as shown in Fig. 

 85. There may be one, two, or several of these spirals 



winding around the 



cell -wall, the num- 

 ber helping to de- 

 termine the species, 

 of which there are many. The plants usually grow iu 

 masses, and especially form those soft green clouds ap- 

 parently floating in the water. They are often attached 

 to submerged objects, but almost as often free. 



Their manner of producing spores is remarkable, but 

 not confined to them, as other Algae have a similar 

 method. The cells of two filaments lying side by side 

 begin, usually at the same time, to throw out from those 

 sides nearest each other a narrow tube. 

 These tubes meet and grow together, so 

 that the two filaments soon resemble a lad- 

 der, the original filaments forming the 

 sides, the tubes being the rounds. The 

 coloring matter then falls away from the 

 cell-walls, and the entire contents of the 

 cells of one filament pass through the rungs 

 of this living ladder into the opposite 

 cells, where the contents of both mingle. 

 From this mixture the spore is formed, 

 one in each cell, and is, when ripe, oval and dark 

 brown. This conjugation, as it is called, and the result- 



