﻿276 Evans: The genus Plagiochasma 



Hepaticae and consist of long tapering cells with thin walls strength- 

 ened by from two to four spiral bands of thickening. Two in- 

 teresting modifications, however, should be noted. In the first, 

 the spiral bands, which are entirely free from one another in most 

 elaters, are coalescent by means of one or more longitudinal bands 

 (Fig. 5, I). In the second, no spirals at all are present but 

 the wall of the elater is uniformly thickened and the cavity re- 

 duced to a narrow median canal (Fig. 8,1). Coalescence of the 

 type found in the first modification seems to be unusual. It was 

 first detected by Miyake (22, p. 223, pi. 3,f. 3) in the remarkable 

 Makinoa crispata (Steph.) Miyake, of Japan, but it has since been 

 observed by Schiffner (29, p. 24) in Neesiella rupestris (Xees) 

 Schiffn., a widely distributed species of Europe and North Ameri- 

 ca, and probably occurs in other genera. The second modifi- 

 cation is apparently confined to the genus Plagiochasma. It was 

 first noted by Gottsche in P. intermedium (10, p. 264) and is 

 mentioned by Stephani as one of the characteristic features of 

 P. japonicum (36, p. 84). Its occurrence has likewise been re- 

 corded by Kashyap (15, p. 320) in the case of P. appendiculatum 

 and P. articulatum, and the writer has observed it in P. eximium. 

 Although the uniform thickening of the elater-wall has been con- 

 sidered a good specific character, it is not a constant feature and 

 must be used with caution. Even in P. intermedium, where it is 

 certainly the usual condition, Leitgeb (18, p. 68) failed to find 

 it in the material which he examined. In the case of P. japonicum 

 Massalongo (21, p. 48, pi. 13, f. ig) has described and figured a 

 var. chinense, based on Chinese specimens collected by Father 

 Giraldi, in which some of the elaters showed rudimentary spiral 

 bands, although most were of the more solid type. Miss Haynes, 

 also, in a series of unpublished drawings based on Japanese 

 material of the same species, collected by T. Yoshinaga, has 

 represented elaters in which poorly developed and irregular bands 

 were present. In P. eximium some of the elaters show spiral 

 bands and others uniform thickenings and there are various 

 gradations between them. In P. appendiculatum the solid type 

 is said to be less common than in P. articulatum, and Kashyap 

 associates it with exposure to dryness during the development of 

 the capsule. In spite of these variations there are certain species 



