VI 



SOME BOTANICAL FACTS ABOUT ALGM 



THE vegetable world is separated into two great divisions: 

 thallophytes, or plants having no distinction of leaf or stem, 

 and cormophytes, or plants which have leaves and stems. All 

 thallophytes that live in the water and are nourished wholly by 

 water are called algce. 



A second great division of plants is into cryptogams, or those 

 that have no flowers, and phanerogams, or those that have flowers, 

 by means of which seeds are produced and successive generations 

 of plant life continued. 



Thallophytes and cryptogams comprise the lowest and simplest 

 vegetable organisms. Algae belong to both these divisions ; to 

 the first because they have neither stems nor leaves, and to the 

 second because they have no flowers. 



The lowest forms of algas are microscopic in size, each indi- 

 vidual being a single cell ; but in the ascending scale they attain 

 curious and beautiful shapes, some growing to a gigantic size 

 and in forms that resemble shrubs and trees. The green surface 

 commonly seen on the' shady side of trees, on stone steps, and 

 in other damp places is one of the species of algae which consist 

 of a single cell. This plant or cell divides, and the separate divi- 

 sions divide and subdivide again and again, and in time the 

 aggregate number is great enough to spread over a comparatively 

 large surface, and thus become visible to the naked eye. This 

 plant, the Plcurococcus vulgar is, is a fresh- water alga. The Pro- 

 tococcus nivalis, or red snow, described on page 33, is a closely 

 allied species. The green and blue-green scums and slimes /on 



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