﻿Evans: The genus Plagiochasma 285 



variable characters, and it is not probable that many writers on 

 the Hepaticae will dissent from Muller's reduction. 



In the present paper several other species are considered 

 synonyms of P. rupestre, and it might appear at first as if the 

 reduction had been carried on in a somewhat wholesale way. In 

 each case, however, the writer has based his opinion on the careful 

 comparison of type specimens with authentic material of P. 

 rupestre from Europe and the Atlantic Islands. It should perhaps 

 be added that most of the species here reduced were proposed at 

 a time when a plant was assumed to represent a new species if it 

 came from a distant or isolated locality. The various species 

 may be discussed in order. 



In P. australe, which Stephani places just before P. elongalum, 

 the following characters are emphasized: the monoicous inflores- 

 cence, the androecium being near the carpocephalum, the pore 

 bounded by five cells, the lack of thickenings in the epidermal 

 cells, the two appendages of the ventral scales, abruptly ligulate 

 in outline, shortly acuminate, as long as the scales. In the 

 portion of the type specimen examined some of these characters 

 were not materialized. The cells of the epidermis, for example, 

 although difficult to see on account of the thick and waxy cuticle, 

 had distinct trigones, and the cells bounding the pores were four 

 in number about as often as five. The radial walls, moreover, 

 separating these cells were strongly thickened. With regard to 

 the scales many of them showed a single appendage, and the form 

 of this structure varied from lanceolate to ovate, the apex being 

 acute. Of course these are only slight deviations from Stephani's 

 account, which was based on Australian material collected by F. 

 von Muller, and they are no more than would be expected in a 

 variable species. Nothing was found in the type specimen which 

 would warrant a separation from P. rupestre. 



In the case of P. limhatum, which Stephani places in his section 

 "a" (see p. 274), although he had not himself examined carpo- 

 cephala, a portion of the original material, likewise in the Mitten 

 herbarium, was examined. Here again nothing was found to 

 warrant a separation from P. rupestre. The distinguishing 

 characters, according to Stephani's account, are the following: 

 the pronounced thickenings in the radial walls of the cells bounding 



