ASPLENIUM TRICHOMANES. 251 



The radicles are black and wiry ; they insinuate themselves 

 into the fissures of rocks, previously so small as to escape ob- 

 servation : in old buildings, this fern certainly promotes decay, 

 by disintegrating the mortar, which, however enfeebled by time, 

 stUl adds in some degree to their strength and durability. The 

 fronds make their appearance in April and May, arrive at ma- 

 turity in August and September, and remain perfectly green 

 throughout the winter. The stipes is about a third as long as 

 the frond, smooth, shining, and, throughout its whole length, 

 of a purplish black colour. The frond is narrow, linear, and 

 simply pinnate : the rachis is green at first, but becomes dark 

 purple : the pinnse dark green and very numerous, irregularly 

 ovate, obtuse at the apex, and more or less crenate at the mar- 

 gin ; they are usually distinct and distant, but are sometimes 

 crowded and each more or less recumbent upon the one pre- 

 ceding it ; they are attached to the rachis by their stalk only, 

 and when the frond approaches decay, the pinnse fall off like 

 the leaves of phsenogamous plants, leaving the rachis naked ; 

 and these, together with the stipes, being very durable, remain 

 from year to year, and become a dense tuft of denuded bristles. 

 The pinnules vary from the size of those represented at page 

 249, to that of the detached ones in the same figure, intended 

 to illustrate the fructification. The lateral veins are forked 

 soon after leaving the midvein (see fig. a), the anterior branch 

 bearing a linear cluster of capsules almost immediately after 

 the division ; this cluster is at first covered by a long, linear, 

 white, membranous involucre, (see fig. h) ; as the cajisules 

 swell this becomes obliterated, and the clusters, which are dark 

 brown, become nearly confluent in two series (see fig. c), which, 

 however, very rarely unite over the midrib : the clusters are 

 ten or twelve in number. 



This fern is, generally speaking, constant in its form, and 

 lather remarkable for its uniformity of appearance. I have, 



