TAXONOMY 
231 
to more elevated bodies in which the net-like structure of the plas- 
modium is preserved ( plastnodiocarps ) to stalked sporangia (spore 
cases). All of the fructifications, however, produce spores. Dur¬ 
ing wet weather amoeboid protoplasts {swarm spores ) escape from 
the spores, each developing a single cilium and moving actively 
about. In time the cilia disappear and these swarm spores coalesce 
in smaller then larger groups to form a plasmodium. 
SUBDIVISION III .—ALGJE 
Low forms of thallophytes of terrestrial and aquatic distribution 
consisting for the most part of single cells or rows of single cells 
joined end to end to form filaments. The higher forms, however, 
possess structures, which might be compared to stems and leaves of 
higher plants although more rudimentary in structure. They 
contain chlorophyll or some other pigment, and so can use the C 0 2 
and H 2 0 in the same manner as higher plants, e.g., in assimilating 
and providing for their Own nutrition. Archegonia are absent in 
this group. 
Class I.— Chlorophyce^e, the Green Alg,e 
Green algae are unicellular (sometimes motile), filamentous, 
colonial, or sheet-like water plants characterized by the presence of 
solitary, or numerous chloroplasts in the cells, which compose the 
thallus. These chloroplasts vary considerably in form, being in 
some cases spiral bands, in other star-shaped, in others like a napkin 
ring, and in others granular. In the chloroplasts of most green 
algae are pyrenoids, which consist of a central crystalline portion 
of protein (aleurone-like) surrounded by a starchy envelope of 
variable magnitude. These are called starch centers and the starch 
is frequently in the form of rounded, or angular grains. The nutri¬ 
tion of these algae is autotrophic. There is a definite nucleus present, 
but in the coenocytic forms the nuclei may be many within the 
confines of the cell wall. The motile cells have one to many cilia, 
as likewise some of the reproductive cells. Reproduction is by cell 
division, the formation of zoospores (motile cells), by zygospores 
