12 



Illinois State Laboratory of Natural History. 



that is to say, genetic relationship. A creditable attempt is 

 made by Prof. Bessey in his excellent Botany (p. 568) to ar- 

 range the primary divisions with reference to descent. It was 

 a fancy of Mr. Austin, expressed in his MSS., as well as 

 hinted in his publications,* that the hepatics were only a high- 

 er development of some form of freshwater algae, and that the 

 ferns, in turn, were a higher development of the hepatics. In 

 a generalized sense this is likely to prove nearer the realm of 

 fact than that of fancy. Unfortunately few of the earlier 

 forms have been preserved in a fossil state to offer a clue to the 

 affinities of primordial types. 



Relation to Mosses. Whatever be the origin of the 

 members of this group, or however the earlier representatives 

 may have been allied to lower forms, the hepatics with the true 

 mosses (Musci) at present form a somewhat specialized group, 

 clearly marked in their methods of growth as well as in their 

 reproductive characters. These two were early associated to- 

 gether in a sub-class known as " Cellular Acrogens," but are 

 now more explicitly and appropriately named the Bryophyta 

 (Gr. bruon, moss, phuton, plant), i. e., mosses and their allies. 



The distinguishing characteristics of the two allied groups 

 may be brought out more clearly by the following parallel ar- 

 rangement: 



Musci. 

 1. Plant body always a leafy 



HEPATIC^. 



1. Plant body varying (in 

 different species) from a thal- 

 lus to a leafy axis. 



2. Stems bilateral, consist- 

 ing of an upper and a lower 

 side distinct in appearance and 

 structure. 



3. Leaves 2-ranked, often 

 with rudiments of a third 

 (amphigastria), never with a 

 midvein. 



4. Root hairs unicellular. 



axis. 



2. Stems not bilateral, uni- 

 formly developed. 



3. Leaves 3-many (some- 

 times 2-), ranked usually with 

 a midvein. 



4. Root hairs usually com- 

 posed of a row of cells. 



* Bulletin Torrey Botanical Club, VI, 306. 



