920 PROFESSOR W. C. WILLIAMSON AND OR. D. H. SCOTT ON THE 
arrangement of the leaves in the heterophyllous species of Ranunculus, of the sub- 
genus Batrachiwm. Several authors have inferred that Sphenophyllum was of aquatic 
or at least semi-aquatic habit. The anatomy, however, as other authors have already 
pointed out,* lends no support to such a view, for in all cases the xylem is extremely 
well developed, whereas its reduction is one the most constant characteristics of 
aquatic plants. 
~ The species which we are about to consider are three in number : 
(1.) Sphenophyllum plurifoliatum, identical with the Asterophyllites spheno- 
phylloides of W1tt1aMson (Parts 5 and 9)... This includes the Oldham specimens. 
(2.) Sphenophyllum insigne, the Asterophyllites insignis of the memoirs above 
cited. To this the Burntisland specimens belong. In these two we know only the 
vegetative organs. 
(3.) Sphenophyllum Dawsoni. This is the Bowmanites Dawsom of previous 
memoirs,t and the Volkmannia Dawsoni of Binney. The specimens of this form are, 
with one exception, limited to the fructifications. 
We will begin with the Oldham species, S. plurifoliatum, which, in its internal 
structure, agrees most nearly with the species described by other authors. 
1. SPHENOPHYLLUM PLURIFOLIATUM, NOBIS. 
Although this form has not been identified with any of the species known as 
impressions, yet the fragments showing structure are sufficient to give also a general 
idea of the external morphology. 
The stems are conspicuously jointed with somewhat tumid nodes.{ The internodes 
are of considerable length, amounting to about 1 centim. in one of our specimens,§ 
which shows two nodes, but no doubt much more in others. 
In no case is a complete whorl of leaves preserved; judging, however, from 
specimens such as C.N. 874,|| in which the bases of 6 leaves are shown, the total 
number in the verticil could not have been less than 18, and may even have 
reached 24. The leaves are sometimes preserved for a considerable part of their 
length, exceeding that of the internode. They remain linear in form throughout, so 
far as can be seen, and there is no distinct evidence for their dichotomizing, though 
they may have done so at some considerable distance from the base.{ 
The cortex of the young stems, as shown in transverse sections, has a very charac- 
* See Sous, ‘ Fossil Botany,’ p. 344. 
+ Wituamson, “ Organization,” Parts XVII. and XVIII. 
t See Witrramson, “ Organization,” Part V., Plate 3, fig. 15, and Plate 1, fig. 5. 
§ CO.N. 904. 
|| Figured in Wintiamson, loc. cit., Part V., Plate 3, fig. 16. 
4 M. Zmit.er has shown that truly linear leaves also occur in S. cuneifolium, Sturn. See his paper in 
‘Mém. de la Soc. Géol. de France; Paléontologie,’ Mém. 11, p. 13, 1893. 
