THE COMMON POLYPODY. 63 
various degrees of marginal division in the primary lobes, showing 
a tendenoy towards the more highly developed bipinnatifid varieties 
represented by semilacerum and cambricum. The most simple con- 
dition of this abbreviated and widened form, in which the apices 
are usually acute and the margins finely serrated, is almost or quite 
identical with the North American plant called P. virginianum, and 
nearly so with the Madeira plant called P. canariense in gardens; 
it is when deeply crenato-lobate, that this type of variation, which 
also sometimes varies with oblong sori, approaches the more highly 
developed or compound forms above alluded to. 
We have thus indicated two different types of development among 
the numerous variations of the Common Polypody. In one of these 
the narrow elongate outline of the normal form is more or less 
preserved ; and in the other, a tendency to develope breadth rather 
than length, results in a frond of broad outline comparatively short. i 
The constancy of the varieties, as tested by cultivation, varies 
considerably according to the mode of treatment, and depends much 
upon whether they are kept confined or exposed ; it is also influ- 
enced by the circumstance of the plants being established or other- 
wise, recently disturbed plants often running out or reverting to the 
normal state, but again assuming the character of the variety as 
they get established at the root. The only kinds, perhaps, that 
are unvarying in their characters, under all circumstances, are 
omnilacerum and cambricum. 
Typal or oblong-fronded Series. 
1. acutum (M.). This variety has the lobes without serratures, 
and narrowed gradually to a longish taper point. In its most 
marked condition it is not a common plant, but is very elegant, the 
fronds being rather broader than the common form of the species. 
Other less marked forms are. not so much tapered, and are, more- 
over, slightly serrulate, approaching towards the acute-lobed state 
of the normal form. We have this variety from two localities in the 
_ neighbourhood of Guildford, Surrey; and from Cornwell, in Oxford- 
shire ; and Mr. Clapham reports it from Settle, Harrogate, and 
Helmsley, in Yorkshire. [Plate II A.—Folio ed. t. 1 E.] 
2. bifidum (Franc.) This has the lobes generally bifid or two- 

