253 
Affinities of Per cinema and Diacalpe . 
Engler and Prantls ‘ Natiirliche Pflanzenfamilien ’, where habit drawings of 
the sorus by Diels are also produced. In ‘ Phil. Trans. ’, vol. cxcii, 1899, P 57 > 
Professor Bower has given a description of the sporangium from Herbarium 
material. F. Bauer’s drawings in the ‘Genera Filicum’ and Professor Bower’s 
drawing (loc. cit., Fig. 9a) give representations of the sporangia. The sorus 
has never been adequately figured. Bauer’s figures give no real idea of the 
nature of the receptacle, and, as Professor Bower remarks, ‘suggest a regularity 
of orientation, which is not, however, to be recognized as constant in 
Herbarium specimens. 5 
The sorus is superficial in insertion and stalked. The stalk springs 
from one of the lateral veinlets on the under side of the pinna, and generally 
grows out for one millimetre or longer, vertically from the leaf. The sorus 
is spherical and, as Wallich remarks, 4 about the size of a Coriander seed ’. 
The youngest stages have, unfortunately, not been available. The material 
sent from Calcutta had upon it only mature or almost mature sori. And 
the living plant which accompanied this material, and which is now 
growing in the Botanic Gardens in Glasgow, has, during the two years it 
has been there, produced no sori. From the youngest sori available for 
examination it appears as though the indusium completely encloses the sorus. 
But at one point, close to the junction of the stalk with the indusium, 
a minute pore can be seen on the outside of the sorus. This forms a very 
narrow slit leading into the interior. Except at this pore, the indusium is 
quite entire, giving the outward impression of an unbroken covering for the 
sorus. It is essentially a cup, developed unequally on its two sides and 
contracted at its rim, which is turned inwards (cf. Fig. 15). When the sorus 
is mature a series of cells across the top breaks down, and an irregular 
crack is formed from one side of the sorus to the other. The two flaps of 
indusium thus formed bend back, exposing the sporangia within to the outer 
air. In this opened condition the resemblance to the sorus of Cyathea is 
remarkably close and convincing. It is this opened sorus which has been 
drawn by Bauer. 
The indusium is made up of a single layer of cells, except just at 
the point of insertion on the receptacle, where it may be two layers in 
thickness. The cells are triangular or quadrangular in outline with tri- 
angular thickenings at their corners, giving the whole indusium a lace- 
like appearance. The receptacle is distinctly elongated, and occupies about 
one-half of the cavity covered in by the indusium. A series of tracheides 
runs into the receptacle from the stalk, and they then spread out in 
fan fashion just above the point of junction of receptacle and indusium 
(Fig. 13). This vascular supply passes right through the stalk of the sorus 
in a median direction, and merges into the vascular supply of the vein of 
the pinna. 
On this elongated receptacle, which is distinctly of the Gradate type 
