CHAPTER XVI 
THALLOPHYTES: ALGJE 
152. General characters. Thallophytes are the simplest of 
plants, often so small as to escape general observation, but 
sometimes with large bodies. They occur everywhere in 
large numbers, and are of special interest as representing 
the beginnings of the plant kingdom. In this group also 
there are organized all of the principal activities of plants, 
so that a study of Thallophytes furnishes a clew to the 
structures and functions of the higher, more complex 
groups. 
The word " thallus " refers to the nutritive body, or 
vegetative body, as it is often called. This body does not 
differentiate special nutritive organs, such as the leaves and 
roots of higher plants, but all of its regions are alike. Its 
natural position also is not erect, but prone. While most 
Thallophytes have thallus bodies, in some of them, as in 
certain marine forms, the nutritive body differentiates into 
regions which resemble leaves, stems, and roots ; also cer- 
tain Bryophytes have thallus bodies. The thallus body, 
therefore, is not always a distinctive mark of Thallophytes, 
but must be supplemented by other characters to determine 
the group. 
153. Algae and Fungi. It is convenient to separate Thallo- 
phytes into two great divisions, known as Alga and Fungi. 
It should be known that this is a very general division and 
not a technical one, for there are groups of Thallophytes 
which can not be regarded as strictly either Algae or Fungi, 
but for the present these groups may be included, 
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