56 N. Bancroft. 
frequent presence of parenchymatous cells separating the centri¬ 
fugal xylem from the protoxylem is due to the disappearance of the 
primary centrifugal elements. It is, at any rate, clear that if 
Chodat’s conception of the primary wood of Lyginopteris be the 
correct one, the similarity between the bundles of this type and 
those of recent Cycads, as described by Messrs. Le Goc and Marsh, 
is only apparent; the difference in organisation between the two 
types is at once seen by a comparison of Figs. 132 and 133 in 
Scott’s “ Studies.” As Weiss points out, “Chodat’s criticism seems 
sufficiently weighty to demand a careful reconsideration of the 
structure and affinities of the Lyginodendreae ” (18, p. 6). 
Turning to the second group of Pteridosperms, those of the 
Medullosean alliance, we find as its basal and simplest form Sutcliffia 
insignis, two specimens of which are at present known. The first 
specimen was described by Dr. Scott in 1906 (13, see also 14, p. 
447), and in 1912, an account was given by Dr. de Fraine (3) of a 
second, evidently representing an older stage than the first. Both 
specimens are of Lower Coal Measure age. This species is con¬ 
sidered to represent an important stock, so far as evolutionary 
tendencies are concerned. 
In vascular anatomy, Sutcliffia is very similar in type to 
Heterangium (Fig. 6). There is a single stele without pith, the 
central part consisting of strands of tracheides mixed with con¬ 
junctive parenchyma. In Sutcliffia , however, the protoxylem groups 
are exarch, instead of mesarch as in Heterangium. The secondary 
xylem, the tracheides of which bear multiseriate pits, is locally very 
Fig. 6. —Sutcliffia insignis. Outline of vascular strands. The broken line 
represents the limit of the tissues; the triple lines represent arcs of secondary 
cortex, a, /3, y, meristeles ; P, protostele ; E, cxtrafascicular strands ; It, leaf- 
traces. (Adapted from de Fraine, 1912). 
