112 DICRANACE^E. 



15. Dicranum strictum Schleich. (Tab. XIX. A.). 



Slender, in bright or yellowish green tufts, resembling D. 

 flagellare, but with the stems fragile, the leaves erect or spread- 

 ing, straight or slightly flexuose when dry, not crisped, very 

 fragile, with the apex usually broken off ; from a narrow 

 lanceolate base finely canaliculate-subulate, entire or almost so, 

 nerve narrow at base, about -f of width of leaf, smooth at back 

 above ; cells at angles lax, brown or hyaline, forming moderately 

 distinct auricles ; usually, but not always, a few narrower cells 

 intervene between these and the nerve ; basal cells elongate- 

 rectangular, thin-walled, 4-8 times as long as broad, gradually 

 becoming shorter above, very shortly rectangular or almost 

 quadrate near the summit, smooth at back. Capsule oblong- 

 cylindric, rather small, smooth ; lid subulate, straight. 



Hab. Old rails and trunks of trees, rarely on walls ; very rare, and sterile in 

 Britain. Near Abbot's Bromley, Stafford (Bloxam) ; Bathfield Park, Staffs. , etc. , 

 (Bagnall). 



Bloxam's plant was recorded as D. viride, and is described by Braithwaite and 

 our other authors under that name. Mr. Bagnall has however kindly sent me one of 

 Bloxam's original specimens, together with specimens gathered by himself in one or two 

 other localities in the same district (one from a mud-capped wall near Alton, Staffs. !), 

 and an original type specimen of Sullivant's of D. viride ( Campylopus viridis Lesq. 

 and Sull. ) ; and after carefully comparing these and other specimens of D. strictum 

 and D. viride, I have no hesitation in saying that all our British specimens belong to 

 D. strictum. In D. viride the areolation of the whole leaf, almost to the auricles, is 

 very small, firm and short, the cells even close to the base being hardly twice as long 

 as wide, and almost all are chlorophyllose. On the other hand D. strictum has a 

 much longer areolation throughout at least the greater part of the leaf, all the cells of 

 the leaf-base being elongated, and for a long distance upwards from the base free of 

 chlorophyll. All our plants agree exactly with the latter, with perhaps a slightly less 

 clear demarcation of the basal auricles. The basal cells are quite as long and narrow 

 throughout the whole expanded part of the leaf, and show no approach to the short, 

 chlorophyllose, firmer-walled cells of D. viride. Husnot gives a further distinction, 

 viz. , that the wide auricular cells of D. viride extend to the nerve, while those of D. 

 strictum do not occupy the whole width of the lamina, a few rows of narrower cells 

 intervening between them and the nerve ; I am inclined to doubt whether this distinc- 

 tion is a perfectly constant one ; but so far as it goes it distinctly supports the view 

 taken here, our British plants never showing the auricles extending markedly to the 

 nerve as in D. viride. The leaves too, though slightly crisped when dry, are .much 

 less so than in that species, and even the amount of curling which is present is chiefly 

 accounted for by the plants being for the most part young. Mr. Bagnall's later 

 gathering, from Alton, in which the plants are older, show the typical straight, rigid 

 leaves of D. strictum. 



Bloxam's specimen is mixed with a little Dicranoweisia cirrata, and it seems just 

 possible that a leaf or two of this may have been examined with the Dicranum, and 

 have given rise to a supposition that the basal areolation was variable in character ; at 

 any rate the cells in that species have a marked resemblance to those of D. viride, 

 although the basal angular cells are less distinct. 



It may be noted that quite recently, indeed since the above was written, M. 

 Camus has published a. paper showing that the French plant, hitherto recorded as 

 D. viride, from Coetquen (Cotes-du-Nord), is really D. strictum, a species which he 

 remarks has hitherto been considered absent from the lowlands of middle Europe. 



