Evolution of Plants 343 



and the hepatics. All existing mosses likewise advance to a 

 higher degree of specialization. So far as we can judge from 

 existing examples, three distinct groups — the Sphagnacete or 

 bog mosses, the Andreseacese or mountain mosses, and the 

 Bryacese or common mosses — early branched off from an an- 

 cestral type with radial branching that was intermediate be- 

 tween Coleochcete and protobryaceous organisms. 



Here the germmating oospore has produced, instead of a 

 swarmspore cell, a protonemal cell that has elongated and 

 undergone septation. On it as on the swarmspore tube of 

 Coleochcete, an outgrowth has become enlarged to form a multi- 

 cellular gametophyte, that has branched radially as in C. 

 pulvinata, but has advanced on the latter in that the main 

 axis has become a multicellular radial structure, while the 

 lateral filaments have subdivided and broadened out into 

 spirally disposed leaf -like growths. Similar advance in anther- 

 idial and oogonial structure has taken place as in primitive 

 hepatics, but the fertilized egg has divided into a sporophytic 

 mass that in complexity and irregular apical rupture resembles 

 types like Marchantia, and which is still retained in Phascum 

 or related simple genera. 



Before leaving the Hepaticse and Musci it may be pointed 

 out that no single representative of either seems ever to have 

 adopted a marine life. Riella Paulsenii is a submerged brack- 

 ish-water species of interior x\sia, that belongs to a fresh-water 

 genus of hepatics, while such moss genera as Fontinalis and 

 Hypnum aduncum var. gracilescens seem in structural detail 

 to indicate that they have been migrants from a terrestrial 

 to a fresh- water environment. The usually soft, slippery, 

 and elongated growth, the browTiish green color, and the rapid 

 dessication that occurs on exposure to the air for a few hours 

 or days, in such aquatic genera as the above, are combined 

 proof of environal action and proenvironal response, in the 

 return of what had become a land type back to an aquatic 

 existence. 



In spite of persistent efforts put forth by many workers, 

 during the past half century, to bridge over the great mor- 



