— 
CHAPTER XX 
TYPES OF CRYPTOGAMS; THALLOPHYTES 
258. The Group Thallophytes.—— Under this head are 
classed all the multitude of cryptogams which have a 
plant-body without true roots, stems, or leaves. ‘Such a 
plant-body is called a thallus. In its simplest form it con- 
sists of a portion of protoplasm not enclosed in a cell-wall 
and without much of any physiological division of labor 
among its parts (Fig. 125). Only a little less simple are 
such enclosed cells as that of Plewrococeus (Sect. 278) or 
one of the segments of Oscillatoria (Sect. 268). The most . 
complex thallophytes, such as the higher algz and fungi, 
have parts definitely set aside for absorption of food and 
for reproduction. ‘The latter is sometimes accomplished 
by more than one process and is occasionally aided by 
some provision for scattering the reproductive bodies or 
spores about when they are mature. 
259. Spores. — Before beginning the study of spore- 
plants it is well for the student to know what a spore is. 
A spore is a cell which becomes free and capable of develop- 
ing into a new plant. Spores are produced in one of two 
ways: either asexually, from the protoplasm of some part 
of the plant (often a specialized spore-producing portion), 
or sexually, by the combination of two masses of proto- 
plasm, from two separate plants, or from different parts of 
the same plant. 
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