142 GRIMMIACE^E. 



Hab. Siliceous rocks in mountainous regions ; very rare. Clova (Fergusson). 

 Barren in Britain. Fr. spring. 



One of the most robust of our species ; G. decipiens differs in the rough hairs, 

 shorter leaves and larger apical areolation ; G. robusta in the much shorter, less 

 incrassate and narrower basal areolation ; G. trichophylla sometimes approaches it, 

 but is probably never quite so large in its parts, and the basal cells are less incrassate, 

 less sinuose and wider, and the nerve weaker ; the fruit is quite distinct. 



15. Grimmia Hartmani Schp. (Tab. XXII. I.). 



In wide patches, yellowish-green above, brown below ; stems 

 procumbent, naked at base, rigid, somewhat dichotomous, 

 branches ascending. Leaves patent, frequently, especially the 

 upper ones, falcato-secund, when dry slightly contorted, long 

 (i-i-j lines), pellucid, broadly lanceolate from a wide base, 

 gradually narrowed to an acute apex, the tip denticulate, green 

 or hyaline in a very short hair-point ; one or other margin 

 recurved ; cells of mid-base narrowly rectangular, incrassate, 

 slightly sinuose, about 3-6 times as long as broad, becoming 

 shorter and more sinuose upwards, a few rows at margin shorter, 

 wider, hyaline, with thinner walls ; in upper part of leaf small, 

 rounded, or sinuosely quadrate and irregular; nerve pale, 

 prominent at back ; terminal clusters of brown globular gemmae 

 usually occur conspicuously on small, thin, deformed leaves at the 

 apex of the stems. Dioicous ; capsule oblong, smooth ; calyptra 

 mitriform, lid rostellate, peristome teeth almost entire. 



Hab. Siliceous rocks, not common. On trees, Aber. Fruit not found in 

 Britain. 



This curious and interesting moss resembles some species of Rhacomitrium in 

 habit more closely than those of its own genus, but may generally be recognised by 

 the spreading falcato-secund upper leaves, with very small hair points, and by the 

 terminal balls of brown gemmae, which are usually present and conspicuous ; the 

 areolation is, of course, quite different. The stems are more rigid, and the whole 

 plant less hoary and greener than most of the allied species of Grimmia. The fruit 

 has only twice been found, in Hungary and Corsica. 



The ridges on the back of the nerve described by Juratzka and Braithwaite are 

 usually, I believe, entirely wanting, and the nerve is quite terete. In this, as in 

 several species of Grimmia, when viewed by transmitted light, the centre of the nerve 

 appears very translucent and the sides opaque, giving just the appearance of two 

 lateral ridges, as in Rhacomitrium patens ; but careful focussing shows this to be an 

 optical illusion, which a transverse section confirms. 



16. Grimmia patens B. & S. (Bryum patens Dicks. Rhaco- 

 mitrium patens Hiibn., Schp. Syn.) (Tab. XXII. J.). 



In large dark loose tufts, bright or yellowish green above, 

 black below ; stems decumbent, naked at base, easily separating, 

 repeatedly dichotomous, 1-3 inches long, branches curved, 



