98 THE HISTORY OF CREATION. 



thallus, also called Protonema, still remains in that lower 

 stage of elaboration manifested throughout life by all Thallus 

 plants ; that is to say, stem and leaf-organs have as yet not 

 differentiated, and the entire cell-mass of the Fore-growth 

 corresponds to a simple thallus. The second and more 

 perfect generation of mosses and ferns — the Stem, or Cormus 

 — develops a much more highly elaborate body, which has 

 differentiated into stalk and leaf (as in the case of flowering 

 plants), except in the lowest mosses, where this generation 

 also remains in the lower stage of the thallus. 



With the exception of these latter forms the first generation 

 of Mosses and Ferns (the thaUus-shaped Fore-growth) always 

 produces a second generation with stem and leaves ; the 

 latter in its turn produces the thallus of the first generation, 

 and so on. Thus, in this case, as in the ordinary cases of 

 alternation of generation in animals, the first generation is 

 like the third, fifth, etc., the second like the fourth, sixth, 

 etc. (Compare vol. i. p. 206.) 



Of the two main classes of Prothallus plants, the Mosses 

 in general are at a much lower stage of development than 

 the Ferns, and their lowest forms (especially in an anatomical 

 respect) form the transition from the Thallus plants through 

 the Algse to Ferns. The genealogical connection of Mosses 

 and Ferns which is indicated by this fact can, however, be 

 inferred only from the case of the most imperfect forms of 

 the two classes ; for the more perfect and higher groups of 

 mosses and ferns do not stand in any close relation to one 

 another, and develop in completely opposite directions. In 

 any case Mosses have arisen directly out of Thallus plants, 

 and probably out of Green Algae. 



Ferns, on the other hand, are probably derived from 



