434 Browne . — A Fourth Contribution to our Knowledge of 
As may be seen in Text-figs. 3-7 the vascular system of the cone 
of E . debile consists of a loose network of strands. The tracts of paren- 
chyma are relatively wide, long, and irregular, and many of them 
originate below the cone proper. It may be freely admitted that an 
analysis of the stele of the cone of E. debile in terms of parenchymatous 
meshes, arising in the phylogeny above traces that have departed, is only 
possible by means of a comparative study of the anatomy of the cone in the 
genus. But in the light of such a study the stele of the cone appears to be 
constructed on the same general plan as that of the other species. This 
point will be further discussed later on (cf. pp. 450-1). 
Leaving out of consideration the parenchymatous meshes arising below 
the lowest whorl of sporangiophores, we find that Cones A, C, and D, 
in which the vascular system is fully differentiated, consist of 68, 35, and 32 
sporangiophores, and contain respectively 12, 4, and 5 parenchymatous 
meshes originating within the limits of the cones. In Cones A and C none 
of these was of the first order ; but in Cone D there were three meshes of the 
first order. Most of the meshes become confluent with others. Usually 
several meshes originating separately become confluent, owing to the dying 
out of vascular strands after the departure of traces. This dying out » 
of strands is not confined to cases where the following whorl consists 
of fewer sporangiophores. Within the limits of Cone B (Text-fig. 4) seven 
fresh meshes are initiated. But the development of two more in the mature 
cone is foreshadowed by the linking up through the phloem of (a) the 
strands from which the third and fourth traces of the lowest whorl depart 
and of (b) the strands giving off traces to the second and third sporangio- 
phores of the third whorl. Had the differentiation of metaxylem followed, 
as it most probably would have in due course, the outline of the phloem 
three meshes (two arising below the cone and one above the second trace of 
the lowest whorl) would each have been converted into two meshes of a 
lower order. The new meshes would have been situated above the fourth 
trace of the lowest whorl, above the fifth trace of the second whorl, and 
above the second trace of the third whorl. A considerable width of xylem 
would also have been differentiated near the level of insertion of the basal 
whorl of this cone. Similarly, in Cone E the distribution of the phloem 
indicates that had the cone reached maturity a further development of 
metaxylem would probably have led, by the closure of a mesh originating 
below the cone, to the formation of a fresh mesh above the third trace 
of the lowest whorl. As it is, only one mesh actually originates within 
the limits of Cone E, for it seems clear that the apparent initiation in 
Text-fig. 7 of a fresh mesh between the second and third traces of the 
fourth whorl is deceptive. It is due to the transference to paper of a tran- 
sient phase ; for the development of the later formed metaxylem would 
presumably have led to the filling in of the small gap between the two 
