GENERA. 
21 
tlieca, making afterwards the following pointed remark : — “ This account of 
Pilularia shows that it is incorrect to say of Acrogens that germination takes 
place at no fixed point, blit upon any part of the surface of the spores ; for it is 
quite certain in this instance that germination invariably takes place at a fixed 
spot, which may be pointed out before germination has commenced.” This view 
exactly accords with some experiments I have instituted, and with the remarks 
of Dr. Lloyd, who read a most interesting paper upon this subject, before the 
British Association, in 1836. The statement in Lindley’s ‘Nat. Sys.,’ ed. 2, 
page 416, that the capsule never produces but one plant, is not correct, for if 
the theca be broken and its contents scattered, as many of the large spores will 
germinate as happen to be fertilized.* 
DISTRIBUTION. — “ The solitary species of this order belonging to Britain 
is widely distributed, being found in Devon and Sussex, and extending at 
intervals from those, counties northward to Sutherland. It is either frequently 
overlooked, or is otherwise a scarce plant in the south of England, increasing in 
plenty in the northern counties ; probably the drier climate of the south-east of 
England, causing the small pools to diminish much or entirely to dry up in 
summer, is adverse to the existence of a plant that is adapted to grow within the 
shallow margins of ponds and lakes. Of its range in altitude, little seems to have 
been yet ascertained.” — Mr. Watson’s MS. 
GENERA. 
The first order of the Ferns is conveniently divided into the sub-orders Nudce 
and Indusiatce, according as the sori are naked or covered with an indusium. 
The arrangement of the species into Genera depends upon the shape and position 
of the sori, together with the nature, the adherence, and the manner of opening 
of the indusium, when there is one. In the other orders the same principles are 
adopted, as far as their structure will admit. 
As the orders of the Fern Allies contain each but one British genus, the 
characters of that genus are but a recapitulation of those of the order itself. 
* Thecce on the lacks of the leaves. 
NAKED, OR WITH AN INCONSPICUOUS INDUSIUM. 
Sori linear or oblong, scattered, with an inconspicuous j vmmitis 
indusium ..... j 
Sori round, scattered, without an indusium . . Polypodium. 
Sori linear, forked, without an indusium . . Gymnogramma. 
* Further particulars of these phenomena, in this family as in the others, will be fjund in 
the works of Hofmeister above mentioned. A general sketch of the whole, by the Editor of 
this edition, will be found in the ‘ Reports of the Brit. Association’ for 1851, and another in 
the 'Annals of Nat. History,’ 2 ser., vol. ix, and these contain references to all the original 
authorities. — A. H. 
