PLAGIOTHECIUM. 435 



shining. Branches ascending, straight or lightly curved, brittle ; 

 branch-leaves imbricated in two rows, complanate or secund with 

 the points curved upwards, widely ovate-acuminate or sometimes 

 triangular-ovate , tapering to a long fine acumen which is flexuose 

 and shining when dry, serrulate at margin, especially above, very 

 faintly two-nerved ; margin plane. Cells rather short, 8-15 times 

 as long as broad, linear, slightly laxer at base, at basal angles 

 wider, sub-rectangular, then suddenly large, inflated, hyaline or 

 orange, few, forming very distinct decurrent auricles. Capsule 

 oblong-cylindric, curved, at first smooth, when empty irregularly 

 but distinctly striate, rather small, with a tapering neck ; lid 

 conical, rather obtuse. Autoicous. 



Hab. On the ground and rocks on mountains, rare ; Highlands of Scotland. 

 Fr. autumn. 



Resembling P. silesiacum, to which it is indeed allied, but more slender, with 

 distinctly wider leaves, smaller, striated capsules, and especially characterised by the 

 inflated hyaline cells, clearly marked off from the other basal cells, and forming the 

 decurrent part of the leaf-base. It is somewhat variable in size, mode of growth and 

 colour. 



The specific name striatellum has priority over Miihlenbeckii, and as it has been 

 used in several standard works of this century, as well as in most modern books, I 

 have employed it in preference to the latter name although that is the one by which 

 it has usually been known to British students. 



6. Plagiothecium denticulatum B. & S. (Hypnum denticu- 

 latum L.) (Tab. LV. E.). 



Very variable ; the following description applies to what may 

 be considered the most typical group of forms (sub-spec, sulcatum 

 Spruce). Tufts flattened, pale shining green, especially when 

 dry ; moderately robust, branches ascending, complanate, more 

 or less elongated. Leaves of branches not crowded, sub-distichous 

 and complanate, somewhat spreading, when dry little altered, 

 usually slightly waved but not much shrunken, glossy, large, 

 \-\\ lines long, oval-oblong or widely oblong-lanceolate, shortly 

 acute, scarcely acuminate, rather wide and decurrent at base, 

 with one or both margins very narrowly recurved, plane or more 

 usually slightly concave, entire except at the extreme tip, where 

 there are almost constantly a very few distinct denticulations ; 

 nerve variable, forked, almost obsolete or reaching (one or both 

 branches) to a third the length of the leaf. Cells hexagonal- 

 rhomboid, large, wide, 10-15 times as long as broad, 120-160 f. 

 long, 10-15 [*■ wide, very chlorophyllose, thin-walled ; gradually 

 becoming laxer, more rectangular and pellucid at base, the 

 angular especially large, sub-rectangular, hyaline, decurrent, but 



