The Genus Fissidens ; or, the Flat Fork-Mosses. 355 



THE GENUS FISSIDENS; OR, THE FLAT 

 FORK-MOSSES. 



BY M. G. CAMPBELL. 



The Fissidentes, like their toothed allies which we considered 

 last month, are perennial plants, and grow on the ground, or on 

 rocks, but rarely on the bark of trees. Their foliage, however, 

 bears no resemblance to that of the Dicranums, being, instead 

 of setaceous and secund, flattened, the upper part expanded 

 into a vertical scalpelliform lamina, and inserted in two opposite 

 rows alternately on the opposite sides of the stem, or rachis ; 

 for this arrangement gives a frond-like appearance to the 

 stem. 



Indeed, the peculiar and highly curious structure and dispo- 

 sition of the leaves of this genus very naturally separate it 

 from all other British mosses with which we have any acquaint- 

 ance, while the insertion of the fruit seems to make it a con- 

 necting link between the Acrocarpous and Fleur acarpous sec- 

 tions; the capsule in some species being terminal, in others 

 lateral, arising from a short fertile ramulus, to which arrange- 

 ment Wilson gives the term Gladocarpous. 



The singular structure of the leaves, besides their being ver- 

 tical, consists in an expansion of tissue from the nerve, and a 

 prolongation of one of the wings of the true leaf, making the 

 leaf, on the stem side, double from above the middle to the 

 base, the expanding wing clasping the stem. This is more 

 conspicuous in the upper leaves, the length of the wing gra- 

 dually diminishing, and the lower being almost destitute of this 

 strange appendage. 



The author above named enumerates and describes in his 

 valuable Bryologia Britannica eight species of Fissidens, most of 

 which may be found in fruit during this month. They derive 

 their generic name from the Latin fissus, split, and dens, a 

 tooth. 



Among the most common is Fissidens taxifolius, or the yew- 

 leaved flat fork-moss. It inhabits moist, shady banks, chiefly 

 in a clayey soil. The inflorescence is monoicous ; the gemmi- 

 form barren flower sitting at the base of the fertile stem. The 

 stems are branched, and fasciculate, i.e., with short lateral 

 branches of unequal height; the taller in this instance are 

 about half an inch long ; they are clustered several together 

 from a common rooting base, where both barren and fertile 

 flowers originate. The leaves are crowded, lanceolate, apicu- 

 late, very minutely crenulate, of a light green, not twisted 



