CHAPTER XXIII 
TYPES OF CRYPTOGAMS; THALLOPHYTES 
264. 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. Only a little less simple are such enclosed 
cells as that of Plewrococcus (Sect. 275). The most .com- 
plex 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. 
265. 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 developing 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 protoplasm from two 
separate plants, or from different parts of the same plant. 
Asexually produced spores are sometimes formed, each 
by the condensation of the protoplasm of a single cell, as 
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