﻿262 Evans: The genus Plagiochasma 



algericum, P. Beccarianum, and P. Schimperi, all from Africa; P. 

 coerulescens Nadeaud, from Tahiti; and P. brasiliense, from 

 Brazil. Since 1898 the following new species of Plagiochasma (or 

 Aytonia) have been published: Aytonia Evansii Haynes and A. 

 jamaicensis Haynes, both from Jamaica (13); P. abyssinicum 

 Gola, from Abyssinia (p.p. 62); and P. articulatum Kashyap, 

 from India (15, p. 320, /. 8). It should be noted further that 

 P. italicum was reduced to a synonym of P. rupestre by K. Miiller 

 in 1907 and that this reduction was sanctioned by Schiffner (25, 

 pp. 252, 254). In the review of the literature just given no allusion 

 is made to papers which simply record extensions of range of 

 individual species. 



If, now, the four species of Griffith are ignored and the reduc- 

 tion of P. italicum to synonymy is accepted, the seven species 

 added by Stephani in 1898 and the four subsequently published 

 increase the total number of species of Plagiochasma to thirty-four. 

 Of these species P. rupestre has been recorded from various stations 

 in Europe, Asia, and Africa, and P. elongatum from both North 

 America and Asia, while the others are distributed as follows: 

 Asia, seven species; Africa, ten; North America, six; South Amer- 

 ica, six; Australia and the islands of the Pacific, three. 



The genus is most at home in arid portions of the tropics, 

 many of the species growing on calcareous rocks. P. rupestre, 

 however, extends as far north as the Mediterranean portions of 

 Europe and P. australe (as already noted) was based on New 

 Zealand material. On account of the dry habitats the sperms 

 often fail to reach the archegonia, and even where fertilization 

 takes place the normal development of carpocephala and sporo- 

 phytes may be prevented by periods of drought. Immature and 

 abnormal carpocephala due to such causes have produced much of 

 the confusion in the interpretation of the genus and its various 



Morphology of the Genus 

 Our knowledge of the morphology of Plagiochasma is largely 

 based on the work of Leitgeb (18, pp. 63-68, pi. i), although later 

 writers have added important details. For a resume of the work 

 done on the genus the Inter-Relationships of the Bryophyta by 

 Cavers may be consulted (4)- Recent writers agree in placing 



