











. 82 THE BRITISH FERNS. 
account of the contrast which their dark shining green enduring fronds 
afford in a choice collection of living ferns. Itis said not to thrive 
in the confinement of a close Wardian case. It may be increased by 
division of the crowns of the caudex. The variety acutum is more 
manageable than the common form of the species, under artificial 
conditions. Mr. G. Maw has observed the same habit, and re- 
marks :—“I think acutum will be an easy and very desirable Fern 
to cultivate. In a cold frame it grows with me much more freely 
than Adiantum-nigrum, throwing up fronds all the year round." 
The Black Maidenhair Spleenwort is met with under various 
phases, some of the varieties differing from the type forms in 
certain obvious and well marked characters, while others are only 
of secondary importance. We omit altogether, in this enumeration 
of them, the mere accidental furcation of the frond or of the pinne, 
which sometimes occurs : 
1. acutum (Poll). This is a plant of very distinct aspect, and 
those who prefer to separate it from Asplenium Adiantum-nigrum 
are perhaps correct in doing so; though as there are obviously 
connecting links, which, in a botanical point of view, indicate an 
exceedingly close affinity between the two, we prefer as the safest 
course to consider the one as an extreme variety of the other. 
The texture in acutum is firmer, i. e., harder and less fleshy-coriaceous 
than in the usual states of Adiantum-nigrum, but forms of the latter 
occur which are not readily distinguishable in this respect. The 
caudex of acutum is short, stout, and tufted, like that of Adiantum- 
nigrum, with which the plant also agrees in being fürnished at the 
crown and on the base of the elongated dark purplish-brown stipites 
with striately reticulated scales, lanceolate below and ending in a 
hair-like point. The fronds vary from about six to eighteen inches 
in length including the stipites, and are from about two and a half 
to seven or eight inches across the base of the leafy portion; in 
a fine Irish example before us, the leafy part is eight inches long and 
seven broad, and the stipes nine inches long. They are quite smooth, 
and in outline are sometimes deltoid, or perhaps more correctly 
pentangular, from the apices of the lowest posterior pinnules forming 
additional angles : sometimes ovate, with the point much attenuated ; 

