20 Bower.—Studies in the Phytogeny of the Fi tic ales. VII. 
less regular than the outer. It will be noted that in the series depicted, two 
leaf-traces depart, and two fusions occur between the inner and the innermost 
systems. Thus it appears that one such fusion corresponds to the departure 
of each leaf. 
These facts will be of interest for comparison with those relating to 
P ter is podophylla to be described below. 
Pterideae bi-indusiateae 
or Pteris Series in the Restricted Sense. 
Pteridium aquilinum (L.), Kuhn. 
Turning now to the Pterideae, it is naturally those with an actually 
existent double indusium, included by Prantl under Lonchitidinae, which 
will be taken first. They were held by Prantl himself to be the most 
primitive. 1 Their soral characters link them clearly with the Dennstaed- 
tiinae and Davalliinae, while their simple hairs point to a primitive 
Dicksonioid relationship. They all show a relatively advanced anatomi¬ 
cal condition. There are, however, numerous details which are as yet 
imperfectly known, even in the familiar Bracken. These require elucidation 
before the phyletic position can be approached. Meanwhile it may be 
quoted from Hooker 2 with regard to his §Paesia, which includes them, 
that ‘ according to strict technical characters this group of species, which 
differs from the rest of the genus also in habit of growth, has as good 
a claim to be placed in Lindsayeae as Pterideae ’. Mettenius also re¬ 
marked 3 that * Lindsay a is distinguished from the indusiate species of 
Pteris by its leaf-margin being unaltered, not rolled back so as to over¬ 
shadow both sorus and indusium ’. It will be noted, however, that these 
differences are only minor points of adjustment, not valid differences 
based on initial origin or occurrence of parts. They indicate the near 
relation of the Lonchitidinae to Lindsay a. 
The origin of the receptacle of the Bracken has never been fully 
demonstrated by observation of the actual segmentations. It is true 
the development has been followed by Burck. 4 The opinions expressed by 
him, together with his Figs. 26-8, have been quoted as the basis of subse¬ 
quent statements by Prantl and Diels ; and an excellent descriptive abstract 
is given by Luerssen. 5 But Burck’s drawings cannot be held as convincing. 
Accordingly fresh observations have been made. The material was partly 
ordinary Scottish Bracken ; partly it was of the var. caudatum , collected in 
Jamaica. Their segmentations correspond, and will not be described 
separately. 
1 1. c., p. 18. 2 Syn. Fil., p. 162. 3 Farngattungen, iii, p. 6, foot-note. 
4 Indusium der Varens, Haarlem, 1874. B Rak- Krypt.-Flora, iii. p. 104. 
