GENERAL MORPHOLOGY 399 
The vegetative system of Sphenophvllum consisted of a slender axis 
(Fig. 215), with elongated and fluted internodes intervening between 
successive superposed whorls of leaves, which in the cone, and sometimes 
in the vegetative region, were more or less webbed below. The branching 
of the shoot was irregular and monopodial: the branches were isolated 
and apparently axillary,' though it seems uncertain whether they were 
not actually, as in L£gutsetwm, inserted 
between two of the whorled leaves rather 
than in the axil of one. 
The leaves in each whorl numbered, 
as a rule, some multiple of three, six being 
a frequent number, though as many as 
twelve, or even eighteen, may be found 
in some species. They were commonly 
wedge-shaped, and more or less forked 
in the venation, with very various cutting 
extending more or less deeply between 
the forks. In some of them, and especi- 
ally in the early forms, the leaves were 
divided into linear or even filamentous 
segments (Fig. 216, A, B.). Potonié points 
out? that the earliest forms bad narrowly 
linear, branched leaves, those of later 
occurrence had larger, more broadly wedge- 
shaped, and unbranched leaves: thus the 
size of the leaf increased in the rising 
geological scale, while the branching of it 
fell off. But, on the other hand, a striking 
feature illustrated in the well-known 5. cixer- 
foltum was the heterophyllous character. 
Here on the same plant finely cut leaves 
may be found below and broader, wedge- 
shaped leaves above, while in the strobilus BiG ee 
the leaves are again finely cut (compare  gyynopayliumn sp., branched stem, bearing 
linear and cuneate whorled leaves on different 
Fig. 215). Commonly the members of one pins ‘The branch (a) terminates in a lang 
whorl were equally developed, but in the eee oe ee a odin) 
forms from the Glossopteris Flora, named 
Trisygia, they were unequal. Examples of the leafage of different types of 
Sphenophylls are shown in Fig. 216, a, B, Cc, D. ‘The plants were fixed in 
the soil by diarch roots, which appear to have been borne on the nodes ; 
but the details regarding them are imperfectly known.” The whole plant 
seerns to have been of a weak, straggling character. 
The internal structure possessed greater distinctiveness than the external 
form, and showed a marked secondary thickening: this originated very 
1Scott, Stadzves, p. 82. ? Engler and Prantl, i., 4, p. 516. ’Seott, Stadres, p. 92. 
