A NEW SPECIES OF SPLACHNOBRYUM 83 



chambers between the dorsal plates of the teeth and the inner or 

 ventral plates ; it is this innermost series of plates, formed of the 

 inner walls of this third series of cells highly thickened and deeply 

 coloured, which, being continued upwards above the mouth of the 

 capsule, form the only visible part of the peristome when viewed 

 from without. The number of cells in this third layer is consider- 

 ably greater than the thirty- two of the second, there being two or 

 three of these cells to each of the sixteen teeth. The persistent 

 radial and horizontal dividing walls of these enclosed cells, between 

 the outer and inner plates of the peristome, show, when a tooth 

 is carefully examined from its outer surface, a series of fine vertical 

 and horizontal lines exactly as are seen in the teeth of the peri- 

 stome in Splachnum. On account of this structure (homologous 

 with the peculiar structure of the teeth in Ptychostomum), and the 

 Diplolepideous nature of the lower portion of the teeth, Philibert, 

 I think rightly, retains the genus Splaclmobryum among the 



Splachnacece. 



With this description of the peristome in S. Boivini, I have been 

 able to compare in detail the structure in two species, both in 

 Herb. Mus. Brit. ; the one is S. Spracei C. M. (no. 209 b, Musci 

 Amazonici et A.ndiim,= Wei sia splachnifolia in Mitten, Musci Austr. 

 Americani, p. 141) ; the other is labelled " Splachnobryum ?n. sp., 

 Dominica, Elliott, 238." The peristomes in these two plants agree 

 closely with one another, and appear to be nearly identical, as far 

 as one can judge, with that of S. Boivini as described by Philibert. 

 The inner wall of the second layer of cells forming the dorsal 

 plates of the teeth is probably more thickened and more deeply 

 coloured than in that species, where Philibert describes it as 

 u faiblement color^e." I failed also to observe the median vertical 

 line dividing each tooth in the exserted portion. But the general 

 structure and the relationships of the several layers of cells are 



the same. 



The peristome in the Baldersby plant, however, differs in some 

 respects markedly from the peristome as typified in the three species 

 above described. The outer of the three layers of cells — that 

 forming the capsule-wall — is very similar, except that the inner 

 walls, as well as the outer, are somewhat incrassate and coloured ; 

 the second layer of thirty-two cells in circumference is also very 

 similar, only having the walls frequently somewhat more thickened 

 than in those species. It is the third or innermost layer which 

 shows a marked difference. A longitudinal section of the capsule 

 shows the cells of this layer towards the base or insertion of the 

 peristome to be narrow in the radial direction, as in S. Boivini ; 

 but the two upper cells, which are on a level with the orifice of the 

 capsule, the ultimate one rising a little above it, are very consider- 

 ably enlarged, the uppermost one especially, so as to appear at 

 times almost inflated ; they are thin-walled and perfectly hyaline. 

 Moreover, instead of there being two or three cells opposed to each 

 tooth, there is (in the ultimate row at least) a single cell only, and 

 this being about double the width of the narrow, coloured, exserted 

 portion of the tooth, it appears at first sight, when viewed from 



h 2 



