﻿274 Evans: The genus Plagiochasma 



In case the growing point of the thallus is not used up in the 

 development of the inflorescence the latter becomes a lateral or 

 dorsal branch, and the shoot which bears a series of such in- 

 florescences would be a monopodium and not a sympodium. 

 Such a change from a sympodium to a monopodium would not 

 be unique. Goebel (8, p. 91) quotes similar examples from the 

 inflorescences of the Boraginaceae and from the vegetative shoots 

 of the Vitaceae. And the further reduction from such a mono- 

 podium through Corsinia to Riccia, where the sexual organs are 

 not in distinct inflorescences and where the intercalary growth 

 so prominent in the carpocephala of Reboulia and Plagiochasma 

 has become largely or wholly eliminated, would be easily intel- 

 ligible. 



In classifying the species of Plagiochasma Stephani (37) lays 

 a great deal of stress upon the shape of the carpocephalum. He 

 divides the genus into two groups, "a" and "6." In "a" the 

 carpocephalum is said to be more or less convex; in "&," more or 

 less excavated at the vertex. From the writer's observations this 

 distinction is not constant. In at least one species which Stephani 

 places in division "a," namely P. japonicum, the carpocephala 

 examined were distinctly concave, and even if this condition 

 should be proved exceptional its occasional presence would in- 

 validate Stephani's classification. It is quite possible that the 

 form of the carpocephalum is influenced by external condition, 

 although no experimental evidence can be brought forward to 

 support this idea. 



The sporophyte of Plagiochasma is described in its essential 

 features by Leitgeb (18, p. 67). He calls attention to its well- 

 developed foot and scarcely evident stalk and to the fact that the 

 wall of the capsule consists of a single layer of cells except in the 

 apical portion, which shows a circular region three cells thick. 

 This he regards as a rudimentary lid although it does not separate 

 at maturity as a typical lid would do. The capsule, in fact, de- 

 hisces irregularly and leaves behind a shallow urn with indefinite 

 teeth or lobes around the rim. The cells of the capsule wall are 

 destitute of the annular or half-annular thickenings found in so 

 many of the Hepaticae. Some of them show more or less distinct 

 trigones, but many of them are thin-walled throughout. The 



