RHACOMITRIUM. 155 



7. Rhacomitrium lanuginosum Brid. (Trichostomum 

 lanuginosum Hedw. ; Grimmia hypnoides Lindb., Braithw. Br. 



M. Fl.) (Tab. XXIV. C). 



Growing in large mats, dull green or yellowish-brown, hoary, 

 rigid and fragile when dry ; stems procumbent, 3-/2 inches long, 

 slender, with numerous slender, variously elongated lateral 

 branchlets. Leaves crowded, spreading, often falcato-secund at 

 the summit of the branches, appressed when dry, with the tip 

 flexuose, long, gradually narrowed from near the base to a very 

 long tapering point, the whole upper part forming a broad, 

 beautifully white diaphanous hair-point, often longer than the 

 rest of the leaf, longly decurrent at the sides of the leaf, erose- 

 dentate at margins, papillose on surface, flexuose and undulate 

 when dry; leaf-base oval, slightly plicate; margin revolute 

 below ; nerve thin, broad, and distinct, running into the hyaline 

 point, at the base of which it is chlorophyllose, above becoming 

 hyaline but distinct almost to the apex ; cells in one stratum 

 throughout the leaf, arranged in regular rows, lowest very 

 incrassate, narrow-linear and nodulose, a single row at basal 

 margin of pellucid, not sinuose, narrow cells ; upper cells broader, 

 sinuose, shorter, but almost always at least twice as long as broad, 

 even at the base of the hair, smooth. Capsule on a short, rough 

 seta, arising on a short lateral branchlet, oval or elliptic-oblong, 

 pale brown, finally darker ; calyptra rough at apex ; peristome 

 orange red, the teeth divided to base into two long filiform 

 branches. 



Hae. Dry rocky heaths, wall tops, rocks, etc. Common. Fr. early summer, 

 not common. 



The largest British species of the genus, and quite distinct in habit alone. It is 

 not very variable, but stunted forms occasionally are found which might at first be 

 taken for R. heterostichum, and a variety occurs with very short hair-points ; these are 

 however easily known by the longer, more sinuose upper . areolation and other points ; 

 from R. canescens the smooth' cells of the leaf clearly separate it. 



R. lanuginosum often covers large tracts of barren heathland, in big swollen 

 cushions ; it is one of the few species of the genus which, like the next, are occa- 

 sionally found on the ground and not actually on rock. The hair-point of the leaf is a 

 most beautiful microscopic object. 



The fruit is not very frequently found, but when it occurs it is produced in 

 considerable quantity. The rough seta is unique in this genus. 



8. Rhacomitrium canescens Brid. (Trichostomum canescens 



Timm. ; Grimmia canescens CM., Braithw. Br. M. Fl.) 

 (Tab. XXIV. D.). 



In lax or dense tufts, erect or spreading, dull green, or 

 slightly yellowish ; stems 1-4 inches long, variously branched, 



