SOME BOTANICAL FACTS ABOUT ALGA 27 
The stem-like forms of certain algee are composed of cylindrical 
cells which combine or grow in a longitudinal direction chiefly. 
Sometimes the cells are arranged evenly, in which case the stem 
seems articulated, as in some species of Ceramium. Again, they 
are irregularly placed, so that the stem appears solid. 
The highest types of alge in the differentiation of parts, or 
vegetative forms, are to be found in the Fucacee, of the brown 
seaweeds; the highest in the reproductive development, in the 
red class. 
Reproduction by cell-division, in which the organism itself 
breaks up into two or more individuals, is called vegetative repro- 
duction. Higher forms reproduce by spores, or germ-cells, which 
give rise to new individuals on germination. 
The substance of an alga is more or less firm, according as the 
vegetable mucus or gelatinous matter it contains has more or less 
consistency ; it is membranaceous when the gelatine is scant and 
glossy, gelatinous when it is abundant and fluid, and cartilaginous 
when it is hard. 
Some alge are annuals; a few are perennials, and cast off and 
renew their lamine every season. Many plants present quite a 
different appearance at different seasons of the year, and so are 
often difficult to identify. Those which form spores throw off 
these isolated cells, which sink or are washed to positions where 
they germinate and begin their cycle of life. Many of the spores 
begin their growth at once, without regard to season, so the 
species is ever present. 
