FISSIDENTACEJE.] 66 [Fissidens. 



vanced to account for it. One of these was that the leaf to a certain extent 

 was split vertically to embrace the stem ; but this is not tenable, as each 

 half of the split portion is of equal thickness to the rest of the leaf. Another 

 view which has met with general acceptance is that the double portion alone 

 is the true leaf (lamina vera C. MUELL.), and all the rest is an outgrowth from 

 it, the portion behind the lam. vera being termed lam. dorsalis, and the two 

 wings beyond these up to the apex constituting the lam. apicalis. However 

 plausible this view may appear, it does not satisfy us, for there are species in 

 which the duplicate part is nearly or altogether wanting, e.g. F. dealbatus 

 from New Zealand. The most rational explanation seems to be this, that 

 the additional lobule is of the nature of a stipule, arising on the opposite side 

 of the stem, which has become adnate to the nerve by the whole lower 

 margin, the upper margin being free and parallel to the corresponding 

 margin of the leaf. Lindberg's names for the several parts are clear and 

 simple, and are vaginant lamina for the conduplicate portion, superior lamina for 

 the continuation of this to the apex, and inferior lamina for the whole length 

 of the part below the nerve. 



The small species of the incurvus group present great variation in the 

 position of the male infl., and I am satisfied that no reliable specific character 

 can be founded on it ; a point noticed by Lindberg to some extent confirms 

 this, viz., that in some autoicous species, the male is connected with the 

 base of the female by rhizomatous radicles which in course of time dis- 

 appear, while the male continues to grow on as an independent plant, and 

 the species thus becomes dioicous. This elegant genus numbers 320 species, 

 and besides the British, five others are European. 



CLAVIS TO THE SPECIES. 



Fruit terminal. 



Leaves not bordered. 



Minute, autoicous, lid conic. exilis. 



Robust, dioicous, lid rostrate. osmundoides. 



Leaves bordered. 

 Border narrow, thickened. 

 Nerve reaching apex and then confluent with the border. 



<? axillar, leaf with a short point. bryoidts. 



$ radical, leaf with a long acute point. Orrii. 



Nerve lost at apex. 

 Small species ; leaves acute. 



Dioicous, capsule inclined, leaves very narrow, acute. f>usillns. 



Autoicous, capsule incurved, cernuous. incurvus. 



Autoicous, capsule equal orslightly asymmetric, erect, or inclined, viridulus. 

 Robust species ; leaves rather obtuse. rufulus. 



Border not thickened, of 4 rows of cells. 



Leaves eroso-serrate at apex. serrulatus. 



Fruit lateral. 

 Autoicous. 



<? radical, nerve excurrent. taxifolius. 



$ axillar, nerve lost below apex. adiantoidcs. 



Dioicous. 



Leaves short, with a pale border, serrulate at apex. decipicns. 



Leaves very long, not bordered, nearly entire at apex. polyfkyllus. 



