GLEICHENIACEAE 561 
be the final decision on this point, it is clear that sori of the same type. 
as those of Gleichenia existed at the Carboniferous period, and that in size 
and form the constituent sporangia were like those seen in the living 
species. 
ANATOMY. 
‘There is greater uniformity of anatomical structure in the Gleicheniaceae 
than in the Schizaeaceae; but still there are marked differences within 
the family which have a probable phyletic bearing when placed in relation 
A. 
Fic. 313. 
A =diagram of the tissues of the rhizome of Gleichenia flabellata. X8. Bz=section of 
the stele (somewhat diagrammatic) of G. pectinata. X26. C=part of the stele of G. 
aickotoma. » X 350. (All after Boodle, from Campbell’s Mosses and Ferns.) 
to other characters! In the majority of species the rhizome shows in 
the internodes a centrally placed, solid stele (protostele), consisting of a 
central mass of xylem composed of tracheides and parenchyma, and 
surrounded by a continuous ring of phloem, pericycle, and endodermis 
(Fig. 313 4). There is thus a general resemblance to the structure of the 
rhizome of Lygodium ; but a point of difference is that whereas in Ligodéum 
there is no typical protoxylem, in G/eichenta the protoxylem is represented 
by several distinct groups of spiral elements, which are mesarch. The 
tracheides of the xylem are arranged in chains and groups separated by 
parenchyma: in fact the structure as seen in G. flabellata is strikingly 
like that of Zygodium, except in the matter of the protoxylem. In several 
1The data here embodied are chiefly derived from Poirault, Azz, Sez. Nat. Bot., 
7 Série, T. xviii., p. 170, etc., and from Boodle, 4xx. of Bot., vol. xv., p. 703. 
2N 
