



THE BRITISH FERNS. 
Genus XII: ADIANTUM, Linnews. 
Gen. CHAR.—Sori indusiate, transverse marginal, reniform 
oblong or linear, continuous or interrupted ; the receptacles seated 
on the under surface of the indusium, and proceeding from the 
apices of two or more converging venules. Indusium (inverted 
membranaceous marginal lobe) venulose, sporangiferous beneath on 
the venules, the receptacles therefore resupinate. Veins flabel- 
lately-forked, or forked from a medial costa, the furcations repeated ; 
venules parallel, free, continued in the fertile parts into the 
indusium. 
Fronds coriaceous or herbaceous, simple pinnately or pedately 
divided or supradecompound; pinn® often articulated, usually 
dimidiate with the costa wanting. Stipitesand rachides ebeneous. 
Caudex tufted, or short creeping. 
This is an exceedingly well-marked and easily recognised genus, 
though presenting considerable variety of character in the species of 
which it is composed, which vary from simple and kidney-shaped to 
many-times pinnate with numerous ultimate pinnules. ` 
The technical character of Adiantum consists in the resupinate 
character of the fructification.. The indusium which is an altered 
reflexed marginal lobe, appears to be turned over on the spore-cases 
as is the case in other marginal fruited indusiate ferns, but in reality 
it is not so. The indusium is indeed turned over as usual, but the 
spore-cases are attached to it, on the surface which then becomes 
undermost. In reality therefore, the spore-cases instead of having 
the indusium lying on them, hang down as it were from the 
indusium itself, being apparently upside down, and this is what is 
intended when they are said to be resupinate. 
The species of Adiantum though all agreeing in this resupinate 
character of the fructification, are yet very varied as to their external 
appearance. These external differences, together with some pecu- 

