220 TORTULACE^. 



coma, cirrate-crisped but not very closely incurved when dry, 

 almost exactly resembling those of Tr. flavovirens , but rather 

 shorter. Seta reddish ; capsule oval-oblong, more or less curved ; 

 peristome teeth long, spirally twisted, fugacious. 



Hab. Banks, usually near the sea. Rare and sterile. 



The leaves of this plant so nearly resemble those of Tr. flavovirens that the two 

 species are very difficult to separate when barren ; indeed among almost all the species 

 of this genus there is so much variation and so much intermingling of allied forms, 

 with very slight and perhaps deceptive fruiting characters, that hardly any arrange- 

 ment or description can be quite satisfactory. Thus Boulay points out that the 

 present species is connected with Tr. tortuosum on the one hand and Tr. nitidum on 

 the other by so many intermediate forms that no very clear line can be drawn between 

 them, and at the same time he makes the present plant a sub-species of Barbula 

 fragilis, indicating a still nearer affinity, in his opinion, to that species. 



7. Trichostomum nitidum Schp. (Tortula nitida Lindb. ; 

 Mollia nitida Lindb., Braithw. Br. M. Fl.) (Tab. XXXII. A.). 



In small, dense, rounded cushions, dull or lurid green, dark 

 below. Leaves very fragile, erecto-patent, slightly flexuose, 

 crowded, when dry rigidly circinate-incurved , very closely in- 

 cumbent, the nerve very glossy and shining at the back ; rather 

 short, about 2 lines in length, linear-lanceolate, shortly and 

 acutely acuminate or more suddenly apiculate, margin plane, 

 slightly undulate, not incurved at apex ; nerve strong, greenish, 

 biown in old leaves, excurrent in a very short mucro, prominent 

 at back ; basal cells hyaline, passing obliquely into the shorter, 

 more chlorophyllose cells, above small, rounded-quadrate, obscure, 

 papillose. Capsule oblong-cylindric, peristome teeth short, rather 

 imperfect, very slightly oblique. 



Hab. Rocks and walls, almost always calcareous. Rare. Sterile in Britain. 



The true position of this plant has been the subject of much discussion, upon 

 -which my slight acquaintance with the fruiting plant does not wairant me in pro- 

 nouncing any opinion ; indeed it is probable that it will remain more or less doubtful 

 until an opportunity is afforded of studying the fruit in good condition and in greater 

 quantity. Hitherto it has only been found in two localities, the two plants presenting 

 certain differences of some importance in the structure of their fruit and peristome. 

 Apart from the fruiting characters, moreover, Tr. nitidum exhibits certain variations 

 in habit and vegetative structure, which tend to ally it on the one hand to Tr. 

 Jlavovirens and on the other to Tr. tortuosum ; and it is quite possible that ultimately 

 it may be found necessary to unite it with one or the other. As far as I am aware, 

 however, the variations in question, do not occur, markedly at least, in this country, 

 and the plant as we have it presents characters sufficiently distinct and constant to 

 enable the student to identify it without much difficulty. It is usually more robust 

 than Tr. flavovirens, less so than Tr. tortuosum ; but in habit it is more dense 

 and rigid than either, usually growing in dense rounded cushions, of a darker colour 

 than in either of these, the leaf-margin, plane at apex, not incurved as in the former, 



