Bower. — Studies in the Phytogeny of the Filicates. 387 
inverted, from what known type of Ferns Eu-Blechnum could have arisen, 
while some of the steps towards Lomaria would be inconsistent with a general 
experience in the phylogeny of the Filicales. Finally, a biological probability 
of the change would need to be established of greater strength than that 
advanced above, which explains the progression from § Lomaria to 
Eu-Blechnum. 
ii. Progression towards an Acrostichoid Type. 
Having arrived at a probable view regarding the origin of the Blechnoid 
state, we may now proceed to consider certain further developments from 
it, which are believed to have been phyletically derivative. The first of 
these is the ‘ Acrostichoid ’ type, the origin of which may be illustrated by 
a comparison of such species as B. Pater soni, B. penna-marina , B. filiforme , 
and B. ( Stenochlaena ) sorbifolia. 
(L) Blechnum Patersoni (R. Br.), Mett. 
As originally described, this species was characterized by having 
a simple leaf. It is a low-growing, very tough, and leathery plant, rather 
widely spread from Ceylon to Australia and New Zealand. Cultivated 
specimens frequently show irregular lobing of the strongly dimorphic leaves, 
while through the var. pinnata , and through B. elongatum , Blume, various 
steps may be found to the pinnate type so usual in the genus. It would 
then seem probable that the habit of the species has originated by simplifi- 
cation of the leaf-outline from the common pinnate type of Blechnum. 
The anatomy of Blechnum Patersoni conforms on a relatively simple 
scale to the characteristics of the genus. Transverse sections of the rather 
short stock show the usual dictyostele (Text-fig. 7, a). At the base of each 
