TRICHOSTOMUM. 223 



some rigid and less curved leaves. It is probable that this very curious and interest- 

 ing species will be found to be allied by intermediate forms somewhat closely with 

 Tr. tortuosum, as is undoubtedly the case with some of the other species of the genus. 

 The fruit has only been found in two or three continental localities. 



44. PLEUROCHiETE Lindb. 



Leaves somewhat serrate or denticulate above, from a 

 sheathing base ; hyaline cells at base marginal only, the median 

 coloured. Fertile flowers axillary. Peristome long, slightly 

 twisted, papillose. Dioicous. 



A very distinct genus both in general appearance and in 

 structure, and, as Braithwaite remarks, with something the habit 

 of Leptodontium. 



1. Pleurochsete squarrosa Lindb. (Barbula squarrosa Brid., 

 Schp. Syn.) (Tab. XXXII. E.). 



Yellowish green, \-2,\ inches high, stems flexuose, loosely 

 tufted, often scattered and mixed with other plants, branched. 

 Leaves rather crowded, larger in the coma, squarrose and 

 flexuose from an erect sheathing base ; when dry strongly but not 

 closely contorted, from the wide base quickly narrowed, 

 lanceolate-acuminate, slightly undulated ; margin plane, finely 

 denticulate above the base, near apex more distinctly and 

 irregularly dentate ; nerve strong, reaching to or slightly 

 beyond the apex; median basal cells small, short, firm, 

 rectangular with rounded angles, pellucid, coloured ; the 

 marginal for several rows much larger, thin-walled, hyaline, 

 abruptly passing into the median ones and forming a very 

 distinct hyaline band, gradually narrowing upwards and reaching 

 to or beyond the top of the sheathing base ; upper areolation 

 small, rounded-quadrate, rather obscure, finely papillose. 

 Perichxtia lateral, the bracts numerous, with a longer sub- 

 sheathing base ; seta long, red, paler above ; capsule oblong- 

 cylindrical, rather large, dark reddish brown ; lid shortly 

 rostrate ; peristome red, fragile, forming about a single spiral 

 turn. 



Hab. Sandy and stony shores, and banks, usually near the sea, and almost 

 entirely confined to the South of England. Rare and sterile. Fruiting on the 

 continent in spring. 



The squarrose tapering leaves from an erect and sheathing base, and the general 

 straggling and rather untidy appearance of this moss, together with its accustomed 

 habitat, make this an easily recognised species ; and under the microscope the basal 

 areolation is seen to be quite distinct from that of any other plant of the Order. The 

 serrations are sometimes distinct, but are often too fine to be seen without the 

 microscope. 



