246 THE BIOCOSMOS PARTICULARIZED. 



on. But the prime difficulty in both cases 

 lies with the first designation which is merely 

 negative (non, not) ; hence the strong effort 

 to bring the non-vascular realm into a posi- 

 tive order. Thus arises the division, quite 

 general in today's classification, of the non- 

 vascular Plants into Thallophytes (Thallus- 

 plants) and Bryophytes (Moss-plants), both 

 of which are antecedent stages of the Fern- 

 plants (Pteridophytes). But the latter and 

 the whole succeeding higher Plant-life are 

 vascular, that is, have true organs; their 

 cells have reached the point of an associated 

 cell-organization. A thallus is the primitive 

 Plant which is not yet differentiated into 

 stem, root and leaf, though it often shows 

 the strong impulse to put forth these mem- 

 bers ; it is a lump of life unformed but trying 

 to form itself, in which the Formative Pro- 

 cess of the Plant is implicit, not yet realized, 

 but struggling. The Thallophytes make a 

 large group with many species, which take all 

 sorts of shapes suggestive of the definite or- 

 gans of the higher Plants. The chief interest 

 of the thallus is that it is prophetic of the 

 whole coming vegetal kingdom, being a piece 

 of plastic material in whose manifold vari- 

 ations are foreshadowed (by the artist 

 Psyche) the future shapes of the Plant-world. 

 The two chief classes of Thallophytes are the 



