DICHODONTIUM. 77 



The specific name is hardly an appropriate one, as the leaves are rather opaque, 

 and even the basal cells are far less pellucid than in most of the species of this Order. 



D. pellucidum might be, and indeed has been taken, in some of its forms, for 

 Leptodontium flexifolium, but the latter is usually a more slender plant, with smaller 

 leaves not expanded at the base, less papillose, and of a different texture. 



2. Dichodontium flavescens Lindb. (Bryum flavescens 



Dicks. ; Dichodontium pellucidum var. serratum Schp., Syn.) 



(Tab. XIV. K.). 



Taller, loosely tufted, yellowish green. Leaves more distant, 

 erecto-patent and slightly recurved, but less squarrose than in the 

 last ; when dry twisted but not appressed nor incurved ; longer, 

 from a narrower base gradually tapering to a narrower, less 

 obtuse flat point, faintly undulated ; margin slightly less recurved 

 below, in the whole of the upper part (and often below the middle) 

 coarsely denticulate or serrate. Cells of leaf base more elongate, 

 only a few rows (usually 1-3) at margin quadrate and obscure, 

 sometimes hardly reaching to base, above incrassate, rounded- 

 quadrate, minutely papillose. Capsule erect or nearly so, shortly 

 oblong-cylindric , symmetrical or nearly so, pale brown ; 

 peristome paler, from a very short basal membrane, not papillose 

 nor vertically striate. 



Hab. Beds of mountainous streams. Not uncommon. Fr. autumn, rare. 



The characters derived from the fruit appear to be of good specific value ; the 

 foliar structure is somewhat variable, but the much less papillose cells, the margin 

 sharply serrate to below the middle, and the narrower and more acute outline of the 

 leaf are characters usually markedly present. The basal areolation, when typical, is 

 very different from that of D. pellucidum, but it is unfortunately not constant, the 

 upper leaves especially sometimes hardly differing in this respect from that species. 

 The longer, narrower, more acute leaves as a rule readily distinguish this plant from 

 the above ; still I have found plants with the habit, colour, and leaf form of D. 

 flavescens, but with the structure of the leaves just that of D. pellucidum, while 

 occasionally on the other hand, especially in fruiting specimens, D. flavescens takes a 

 more slender, green form, resembling D. pellucidum. It is not an uncommon plant 

 beside mountain streams, but the fruit is rare ; when present, too, it is often over- 

 topped by the innovations, and so rendered inconspicuous, in both species. 



Tribe 4. Trematodonteas . 



20. TREMATODON Mich. 



Plants with short stems but tall fruitstalks. Leaves very 

 narrow, subulate, smooth; cells rather lax, hexagonal-rectangular. 

 Perichaetial bracts distinct. Calyptra inflated below, rostrate. 



