558 Bancroft.—A Contribution to our 
this fact 1 is uncertain, for in R. cylindrica it is evident that the distribution 
of the two types depends upon the width of the tracheide walls. 2 
There is thus considerable agreement in the organization of the four 
species, and in view of this fact it is interesting to note that the associated 
sporangia in each case are of similar type. 
It is inadvisable to draw any conclusions from the apparent absence 
of a leaf of ordinary Fern type within this group. In B. ramosa there are 
indications that* the frond was much dissected, as in Stauropteris and 
members of the Zygopterideae ; while the presence of small axes asso¬ 
ciated with R. cylindrica suggests incomplete foliar development in this 
species also—a suggestion which is supported by the probable assimilatory 
nature of the outer cortex of the stem and petiole. Smaller axes, again, 
occur in association with the petioles of B. antiqua , but it is as yet 
impossible to say what the exact condition of foliar development may 
have been in these plants; and in any case, similarities or differences may 
have been due to the influences of environment rather than to degree of 
relationship. 
The four species differ to a certain extent in habit. B. antiqua is 
considered by Kidston 3 to have been a scrambling plant requiring support 
for its large leaves, some of which were accompanied by sheathing 
aphlebiae. 4 Seward 5 suggests that the slender plants of B. ramosa , with 
their much branched leaves, were epiphytic in habit; while B. hirsuta 
seems to have been similar, though with larger and less crowded leaves. 
There are indications that R. cylindrica was an ‘ amphibious } plant; its 
dichotomously branched stems were of lax habit and bore few leaves, the 
inadequacy of which is suggested by the development of apparent cauline 
assimilatory tissue. 
These differences, however, are not greater than are to be found 
amongst closely-related types—even within a single genus—at the present 
day. The diversity of habit, and of habitat, amongst the species of 
Polygonum may be mentioned as an example. 
It may be concluded that B. antiqua , R. cylindrica , B. ramosa , and 
B . hirsuta form a group of closely-related species, showing, at least in the 
behaviour of the foliar trace, a gradual transition from a simple to a more 
complex structure. 
Botryopteris forensis , as representative of the French Permo-Carboni¬ 
ferous species, seems to stand a little apart from the group of older British 
species. 
1 Stopes, M. C.: A New Fern from the Coal Measures : Tubicaulis Sutcliffii, spec. nov. Mem; 
and Proc. Manchester Lit. and Phil. Soc., vol. 50, Pt. Ill, 1906. See p. 24. 
Gordon (’ 10 ), p. 400 ; Seward (’ 10 ), p. 436. 
2 Cf. Scott (’ 08 ), p. 326. 
3 1 . c., p. 364. 4 Benson (’ll), pp» 1048 and 1049; Text-figs. 1 a and 1 b. 
5 !• c., p. 441 - 
