PROTHALLUS PLANTS. 97 
part covered by eternal snow, on which no plant could 
thrive—are encrusted by the dry bodies of Lichens. 
Leaving now the Fungi, Lichens, and Algz, which are 
comprised under the name of Thallus plants, we enter upon 
the second sub-kingdom of the vegetable kingdom, that of 
the Prothallus plants (Prothallophyta), which by some 
botanists are called phyllogonic Cryptogamia (in contradis- 
tinction to the Thallus plants, or thallogonic Cryptogamia). 
This sub-kingdom comprises the two provinces of Mosses 
and Ferns. 
Here we meet with (except in a few of the lowest 
forms) the separation of the vegetable body into two 
different fundamental organs, axial-organs (stem and root) 
and leaves (or lateral organs). In this the Prothallus plants 
resemble the Flowering plants, and hence the two groups 
have recently often been classed together as stemmed plants, 
or Cormophytes. 
But, on the other hand, Mosses and Ferns resemble the 
Thallus plants, in the absence of the development of 
flowers and seeds, and’ even Linnzus classed them with 
these, as Cryptogamia, in contradistinction to the plants 
forming seeds; that is, flowering plants (Anthophyta or 
Phanerogamia). 
Under the name of “ Prothallus plants” we combine the 
closely-related Mosses and Ferns, because both exhibit a 
peculiar and characteristic “alternation of generation” in the 
course of their individual development. For every species 
exhibits two different generations, of which the one is 
usually called the Prothalliwm, or Fore-growth, the other is 
spoken of as the Cormus, or actual Stem of the moss or fern. 
The first and original generation, the Fore-growth, or Pro- 
