Bower.—Studies in the Phytogeny of the Filicales . VII. 9 
characters an advance on .S'. rupestris. A transverse section of one of the 
pinnae—which here are fewer in number, but longer than in S, rupestris — 
shows that the indusial flaps are much larger, completely arching in a 
considerable space on either side, while the sporangia are still relatively 
small (Fig. 10). The sporangia when mature appear in the four rows 
characteristic of W\Actinostachys. Prantl has already stated that this is 
the result of displacement of the sporangia of a single marginal row on each 
side. Fig. 11, a , shows a longitudinal section of the marginal series of 
cells of a pinna, from which the sporangia arise in acropetal succession. 
A tangential section of such a marginal series (Fig. 11, b) demonstrates 
Fig. 10. Transverse section of a pinna of Schizaea digitata , showing the indusial flaps 
much larger in proportion. ( x 65.) 
how by alternate displacements, right and left, the two rows of sporangia 
are formed from the single marginal series on each side of the leaf. In this, 
as in the larger development of the indusial flaps, 5 . digitata may be held 
as an advance upon the type of rupestris . 
This marginal origin of the sporangia of Schizaea , and their subsequent 
displacement and the formation of an intramarginal indusial flap which 
takes the appearance of a normal leaf-area, are facts thus fully demonstrated 
for Schizaea. The same was also shown by Prantl in Mohriat The 
sporangium arises from the margin ; but an intramarginal protective flap 
originates below it, and finally takes a distal position as though it were 
a direct continuation of the leaf-surface. The result is that the actually 
marginal sporangium appears, as it becomes mature, to be superficial. This 
is shown in Fig. 12, where the vascular strand is seen to run to a point 
below the sporangial stalk. In some eases it extends beyond it, as noted by 
1 l.c., PI. VIII, Figs. 134, 135, 138, 140, text, p. 43. 
