124 FISSIDENTACE/E. 



8. Fissidens crassipes Wils. (F. viridulus var. fontanus 



Braithw., Br. M. Fl., p. 71) (Tab. XX. I.). 



In dark green dense tufts, often submerged, tall, \-2 inches 

 long, rather rigid, often emitting tufts of red radicles from the 

 axils of the leaves. Leaves oblong-ligulate, shortly and obtusely 

 acuminate at summit, border thick, vanishing below the minutely- 

 serrulate apex, often irregularly nodulose or denticulate, frequently 

 tinged with red; nerve thick, reddish, vanishing in the apex. 

 Cells large, 12-18 n wide, rather lax and irregular, with thin 

 walls, deep green with chlorophyll and opaque. Dioicous. Male 

 inflorescence terminal, conspicuous. Fruit terminal, on a short, 

 thick, reddish flexuose and often geniculate seta, erect or inclined ; 

 lid acutely conical. Spores twice as large as in F. viridulus. 



Hab. Stones in streams, especially in calcareous districts. Not common. Fr. 

 late autumn. 



Although by many authors this is united to F. viridulus, it appears to be a good 

 species, differing not only in the much larger, opaque cells, but also in the form of the 

 leaf apex, which in this is bluntly triangular, sometimes almost rounded, but in the 

 smaller plant is acute and often apiculate. The seta is also thicker, and this must not 

 be looked upon as a necessary consequence of its aquatic habit, since in F. rivularis, 

 equally aquatic, it is particularly slender. It is much nearer F. rufulus, and indeed 

 can sometimes hardly be separated except by the larger, thin-walled cells. I find it 

 abundantly fruiting in Northamptonshire with the capsules exceedingly polymorphous 

 both as to form and direction, sometimes being arcuate as in F. incurvus. 



The apex of the leaf is frequently eroded and may thus appear to be more obtuse 

 than is really the case. 



9. Fissidens rufulus B. & S. (Tab. XX. J.). 



Resembling the last, but with the leaves slightly shorter, 

 broader and more obtuse, almost always with some tinge of red, 

 especially on the nerve and border of the older leaves. Cells 

 smaller, incrassate, more regularly hexagonal, rather obscure but 

 less so than in F. crassipes. Fruit terminal on a paler, more 

 slender seta, the capsule more regular ; lid variable. 



Hab. Stones in mountain streams ; very rare. Fruit late summer, rare. 



The incrassate cells are the chief character by which this may be known from the 

 last. As occurs in other mosses with a somewhat solid leaf texture, the thickening of 

 the cell-walls takes place in the interior of the leaf rather than on the surface, hence 

 if the microscope is focussed on the surface they do not appear incrassate, and their 

 true character is often only seen on focussing lower down. In the present case the 

 thickening matter is so deposited that the cell-lumen is left rounded, while the actual 

 form of the original cell (as it still appears on the surface) is rectilinear and more or 

 less hexagonal. This is best seen in the older leaves ; in the younger ones the cells 

 are rendered rather obscure by chlorophyll granules. The fruiting characters must 

 certainly be considered untrustworthy, as however constant they may be in the present 

 plant (though there is considerable discrepancy in the various descriptions) similar 



