Pteridophytes. Are they vestigial? 237 
In this series of ground-growing forms, the intercalation of 
a peduncle, with small distant scales, between the larger- 
leaved foliage shoot and the definite strobilus, is indicated. 
The question whether the peduncle is directly derived from 
the basal part of the strobilus, or from a specialized part of the 
already sterile foliage-region, may be left open : but as spor- 
angia are not found on it, nor even any vestiges of arrested 
sporangia, the latter seems the more probable source of the 
peduncle. The importance of it in ground-growing forms 
is obvious. 
Group of L. later ale. 
The strobilus is well differentiated from the sterile shoot. 
88. L. dijfusum , R. Br., ‘intermediate between L. laterale and 
L. magellanicum V After clear cases of dichotomy, the one branch 
continues sterile growth, the other is fertile. 
89. L. laterale , R. Br., the same behaviour of the branches is seen, 
but more pronounced : sometimes both branches are sterile : in some 
specimens the successive branches on the same side are fertile, giving 
a peculiar sympodial effect. 
Sub-genus IV. Diphasium. 
The strobilus is well differentiated from the sterile shoot. 
The peculiarity is in the bilateral development of the latter. 
90. L. carolinianum , L. In some forms differs only in minor degree 
from L. clavatum or L. inundatum, as regards leafage; but some forms, 
e. g. L. sarcocaulon , Welw., show extreme cases of dorsiventrality. 
92. L. complanaium , L., often regarded as merely a dorsiventral 
form of L. alpinum. 
93. L . scariosum , Forst., sometimes shows the strobilus fining off to 
an attenuated, vegetative apex, but no complete return to the foliage 
type of shoot. 
94. L. volubile , Forst. A highly specialized, scandent, dorsiventral 
shoot, with definite strobili, which show no return to the vegetative 
type. 
Baker, loc. cit., p. 27. 
