GRIMMIA. 143 



especially when dry. Leaves patent or slightly secund, when dry 

 erect and appressed, from a broad, oval-oblong base, elongate- 

 lanceolate (i-i; lines), tapering to an entire or slightly toothed 

 point, not hyaline ; margin recurved below, slightly thickened 

 above; nerve very prominent at back, strongly two-winged in the 

 upper half of the leaf. Basal cells yellow, narrow-linear next the 

 nerve, with the walls smooth or slightly sinuose, becoming shorter, 

 wider and more sinuose outwards, a few rows at margin shorter, 

 with thinner walls, not sinuose, pellucid but not hyaline ; all 

 becoming rapidly shorter above, sinuosely rectangular, then 

 minute, rounded or transversely elliptical and compressed, very 

 dense, in regular longitudinal rows, 2-3 stratose, all more or less 

 incrassate. Seta rather long, arcuate, yellow ; at maturity erect 

 and flexuose ; calyptra mitriform, lobed ; capsule oval-oblong, 

 rather large, pale yellowish brown, plicate when dry ; lid shortly 

 subulate, straight, usually falling with the calyptra ; peristome 

 teeth long, divided into two filiform branches. Dioicous. 



Hab. Siliceous rocks on mountains. Not common. Fr. spring. 



A very distinct species, resembling in habit slender, dark forms of Rhacomitrium 

 protensum, but of a much softer texture when moist, though somewhat rigid when 

 dry ; the curious double wing at the back of the nerve is quite perceptible with the 

 lens, especially in the dry state, and will serve to distinguish the species from all other 

 plants it may resemble. The ripe fruit is very persistent, and soon has the appearance 

 of being lateral, from the growth of the innovations. 



A few cells at the apex of the leaves are occasionally diaphanous, but I have never 

 seen anything approaching a hyaline point, which Boulay describes as sometimes 

 occurring ; the leaves vary much in the relative acuteness of their points. 



* * Seta erect. 



17. Grimmia Doniana Sm. (Tab. XXII. K.). 



In dense rounded neat cushions, about £ inch in height, 

 greyish green above or almost black. Leaves spreading, appressed 

 when dry, the uppermost longer (1 linej, oblong-lanceolate, 

 terminating in a slightly toothed hair nearly as long as the leaf ; 

 the lower small, muticous ; margin plane, slightly thickened 

 above ; nerve narrow, obscure at apex. Cells at base hyaline, 

 thin-walled, narrowly rectangular, 4-6 times as long as broad, 

 the marginal hardly distinct ; becoming shorter, chlorophyllose, 

 incrassate and sinuose above, in upper part 2-stratose, sinuosely 

 rectangular or sub-quadrate. Capsule on a short, erect seta, 

 hardly elevated above the upper hair-points, pale brown, oval- 

 oblong, small, erect, smooth; lid conical, obtuse; calyptra 



