VI 
SOME BOTANICAL FACTS ABOUT ALG 
HE 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 alge. 
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. Algez 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 alge 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 alge 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 Pleurococcus vulgaris, 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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