Bower.—Studies in the Phytogeny of the Filicales. 497 
its under surface is covered by continuous soral masses on either side of the 
well-marked midrib. It was this feature which Hooker recognized as 
‘ Acrostichoid There is a good deal of variety in the outline of the 
lamina. Hooker was aware of this ; he describes the leaves as ‘ quite 
entire and tricostate, or sub-orbiculate and deeply bicuspidate ’ (1. c., p. 371). 
He notes that specimens from the Loo Choo Islands were mostly with quite 
entire fronds ; and these constituted the var. b , integrifolia , Eat. Both 
forms of leaf may be seen on the same plant (Christ, 1 . c., p. 18 , Fig. 7 ), 
a point frequently met with among the Bornean specimens, in which also the 
entire leaves were in the majority. But they also showed examples of 
greater complexity of form, such as are represented in the photographs 
Figs. 4, 5 . Comparison points towards the conclusion that the more com¬ 
plex outlines are liable to occur in the leaves of the more mature plants, but 
there is no constant evidence of an ontogenetic progression. Fig. 1 shows 
to the right a relatively weak plant, with all its leaves simple; to the left is 
a larger plant with two sterile and one fertile leaf, showing the difference in 
proportion of the two types. Of the sterile leaves one is ovate with a single 
cusp, the other is broadly two-lobed. On other plants it was not an 
uncommon thing to find three distal lobes united below into a broadly 
ovate lamina. Some plants, however, showed regularly the leaf-form 
depicted in Hooker’s often quoted figure ; this is shown in Fig. 3 ; but these 
were in a distinct minority in the specimens from Borneo. Hooker’s 
figure, together with the specific name bicuspe , has in fact stereotyped much 
too strongly a form of leaf which is far from being general for the species. 
Other plants showed still more complex outlines, with irregular dichotomous 
branching. Thus in Fig. 4, one of the leaves is of the two-cusped type, but 
in the other both lobes have branched a second time. This condition is 
shown again in a more complete example in Fig. 5 . 
Comparing this last leaf with leaves of Dipteris conjugata it is at once 
evident that they conform to the same type, a conclusion which the venation 
also confirms. On the other hand, a comparison may also be made with the 
fertile type of leaf of Platycerium , and Fig. 6 shows one of these of P. Hillii , 
which corresponds in the number and relation of its dichotomies very 
closely with that of Cheiropleuria in Fig. 5 . The chief difference lies in 
the continuance of the broad expansion downwards, so that there is no 
distinct petiole. But this is a condition which is still more pronounced 
in the nest-leaves of Platycerium , which have no petiole at all. 
The essential features of the venation are already known from the 
drawings of Hooker, quoted by Diels (E. & P., i. 4, Fig. 175 ). But their 
arrangement at the base of the lamina is shown in Text-fig. 1, drawn from 
a leaf of Cheiropleuria made transparent by eau de Javelle , and mounted in 
Canada balsam. The main veins diverge in two groups right and left of the 
median line, while distally they show bifurcations. An examination of 
