CERATODON. 69 



margin revolute to apex, entire ; the nerve excurrent in an arista 

 or point of varying length ; cells small. Capsule erect or very 

 slightly inclined, ovate-elliptic, rather wide at base, when dry and 

 empty hardly altered, slightly sulcate, the neck not strumose ; 

 lid shortly and obtusely conical. Peristome teeth pale, with few 

 articulations, with very narrow and less distinct borders. 



Hab. Bare places and mud-caps of walls. Rare. Fr. summer. 



The examination of a considerable number of specimens from different localities 

 has convinced me that the present plant should not rank higher than a sub-species of 

 C. ptirpureus at most ; a conclusion arrived at for the most part on account of the 

 existence of a number of intermediate forms linking it, in an unbroken chain, with 

 that plant. Specimens found by me in Scotland in 1883 have the fruiting characters 

 exactly those of C. conicus, but the plant has the purplish hue of the typical form and 

 the nerve is excurrent in a very short point only. Since that time, in a number of 

 localities in Northamptonshire uniformly on the mud-caps of walls in the oolitic 

 districts, I have found plants which, while with the peristome and the foliage of C. 

 conicus (the nerve being excurrent in a point frequently as long as the whole of the rest 

 of the leaf), show a great variation in the capsule, both as regards its inclination and 

 form, the struma, and the lid ; sometimes being barely if at all distinct from ordinary 

 C. purpureas, at others, though more rarely, with capsules almost exactly characteristic 

 of C. conicus, while specimens may be found of nearly every intermediate form. It 

 must be remembered too that the nerve is sometimes excurrent in otherwise typical 

 C. purpureus. 



In the Northamptonshire localities above mentioned, this plant even when barren 

 and growing with the typical form, may be generally recognised with the eye alone, 

 by the denser, neater tufts, with the shorter, aristate, upper leaves forming a comal 

 tuft. 



C. minor Aust. (Lesq. & James, Manual of Mosses of N. America, p. 92) 

 appears to be this plant ; the only difference, according to the description, being that 

 in that moss the leaves are spoken of as serrulate towards the apex. 



17. RHABDOWEISIA B. & S. 



Plants short, inhabiting rock crevices, densely cushioned. 

 Leaves linear or ligulate, not much attenuated at point, short, 

 much crisped when dry, with plane margins ; areolation small, 

 more or less quadrate above. Capsule erect, symmetrical, 

 minute, on a very short seta, striate, not strumose. Peristome 

 small, teeth narrow, subulate, undivided. 



The three plants here included have a distinct habit and in 

 other respects form a natural group, though linked to 

 Cynodontium by C. Bruntoni, which however clearly belongs to 

 that genus. Their short, highly chlorophyllose, plane-margined 

 pellucid leaves abundantly distinguish them, in addition to which 

 they are usually abundantly fertile. 



/Leaves with narrow tapering points, almost entire 1. fugax 



\ Leaves with wider, more obtuse points, serrate 2 



fPlant small; leaves narrow, cells 8-10 p 2. denticulata 



2-j Plant \-\ inch ; leaves broader, more coarsely toothed, cells 14-18 /* 



\ J. crenulata 



