FERNS, FOSSILS AND FUEL 
thallophytes. The name is derived from the Greek word 
thallos , meaning bed or layer, and phyton, meaning 
plant. The thallophytes are a group of plants which 
are composed merely of a layer of plant-substance without 
differentiated tissues and, especially, without woody fibers. 
This stem is divided into two subdivisions, each of 
which is composed of numerous families, genera, and 
species. One of these subdivisions is the algae, or water 
weeds; the other is the fungi, to which mushrooms, molds, 
bacteria, and numerous other groups belong, having a 
low form of development and containing no green plant- 
substance. The possession of this green leaf substance, 
called chlorophyll, is the main distinction between the 
algae and the fungi. 
Under the microscope, chlorophyll grains appear as 
bands, spherical bodies, or variously shaped, saturated 
with a green substance which is the chlorophyll and 
which we can extract with alcohol or benzine. This 
substance makes possible the fundamental chemical 
process of organic life, consisting of the building up of 
organic from inorganic material. The carbon dioxide 
of the air and water is changed, under the influence of 
sunlight, into alcohols, starches, sugars, cellulose, protein, 
albumen, and a host of other chemical substances that 
are the bearers of life. This change takes place only in 
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