Affinities of Per anew a and Diacalpe . 
257 
External Characters. 
The stock is upright, or at first creeping and becoming upright before 
more than twelve leaves have been produced. It is narrower than that of 
Peranema , and is not covered by a dense felt of paleae. The leaf-insertion 
depends on the size of the stock ; in one case the divergence has been found 
to be a fifth, in other cases it is irregular. 
The leaves are large, from two to four feet long, with a long petiole, 
and are decompound and herbaceous. The lower part of the petiole is 
covered with broad, brown membranaceous scales. Similar but smaller 
scales appear together with hairs as little tufts at the axils of the primary 
pinnae on the younger branches. The frond is tripinnate, the primary 
pinnae often being nearly opposite. The rachis of the frond and that 
of the pinnae bear short scales and hairs of a single long series of cells. 
Long hair-like scales also appear on the upper surface of the leaf above the 
veins. Unicellular glands are found on the petiole and rachis among the 
scales and hairs, but no glands are present elsewhere on the leaves. On 
older leaves the scales and hairs disappear from the raches, which are then 
quite smooth. 
The primary pinnae are lanceolate, the secondary pinnae being obtuse 
and oblong-cuneate ; the lower pinnules are deeply pinnatifid and somewhat 
decurrent, so that the rachis of the ultimate pinna is generally winged. 
The venation is open ; the veins are simply pinnate, and the veinlets are 
undivided, not reaching quite to the margins of the leaflets. 
The sori are produced superficially on the under surface of the leaf, 
usually on the lower anterior veinlet of each segment, at a point below its 
termination. Usually there is only one sorus on each veinlet. The sorus 
is apparently sessile, but it is not strictly so, being seated on a slightly 
elevated point, from which the entire sorus can be freely removed without 
rupturing the base of the indusium or receptacle. The indusium is at first 
quite entire, completely enclosing the sorus. Its texture is very coriaceous. 
It ultimately breaks irregularly at the apex, and opens by two or more 
valves. The receptacle is short and is covered by a large number of 
sporangia, irregularly arranged within the sorus. 
The sporangium is long-stalked, with a somewhat bulky capsule, and 
an annulus vertical in insertion but slightly twisting to one side as it crosses 
the capsule. The spores have warty superficial markings. 
Internal Structure. 
The transverse section of the stock very closely resembles that of the 
stock of Peranema cyatheoides. The meristeles are inserted in the same 
fashion, and the leaf-traces bear the same relation to the main vascular 
system as do those of Peranema . The vascular system is in Diacalpe also 
