448 The Living Plant 



As one might expect, there are plants supposed to be Algae 

 which really are not. Thus the Eel-grasses, the Pond-weeds, the 

 Duck-weeds, and many other Water-weeds, are Flowering Plants 

 which have adopted a life in the water, and therefore an Alga-like 

 aspect. They can be told by their flowers which they bear in 

 their season, and which separate them sharply from the spore- 

 bearing Algae. 



We turn now to consider the origin and evolution of these 

 Algae, together with their classification. If evolution is a fact, 

 and all evidence appears to agree that it is, then classification 

 must be an expression of genealogical descent, and expressible in 

 a genealogical tree, comparable with the kind which some people 

 are fond of constructing to show the genealogical ramifications of 

 human families. Such a tree, for the great primary groups and 

 their principal subdivisions, is presented in our accompanying 

 diagram (figure 177), and the mode of its construction is as follows. 



First as to its most ancient, or lowermost, part. We have good 

 reason for believing, as the chapter on Protoplasm suggested, that 

 our present green plants were preceded in time by a colorless 

 kind, which, though without chlorophyll and of the utmost 

 simplicity, could yet make their own food from carbon dioxide 

 and water by using the energy of chemical oxidation of soil min- 

 erals in place of that of the sunlight. We have precisely such 

 chemosynthetic organisms, a kind of soil Bacteria, still living on 

 the earth at this day; and they are doubtless the lineal descend- 

 ants of the ancient forms, which probably lived in the mud of 

 shallow seas that may be full of them yet. These ancient chem- 

 osynthetic organisms were neither animal nor plant but both and 

 between, — the dawn of the kind of plant-animal forms sometimes 

 called Protista; and therefore I suggest that we call them Eo- 

 protista. These Eoprotista, therefore, form the base of the gen- 

 ealogical tree. Then, like all later groups, they must have ex- 

 panded, developed, varied, evolved, thus originating a great 

 many branches, of which the greater number perished, and only 



