412 BOTANICAL GAZETTE (DECEMBER 
the younger English anatomists to hunting for such evidence in 
fern seedlings, success has not crowned their efforts. Moreover, 
if the collateral type of bundle really be primitive for the existing 
ferns, we should expect to find this condition present in the 
bases of their foliar organs. It follows, from all the considerations 
mentioned above, that the absence of the concentric condition in 
the seedlings of the comparatively few existing ferns showing 
collateral organization in their adult cauline system constitutes 
no valid argument against the primitiveness of the concentric 
bundle for the stem of these and of ferns in general. The evidence 
considered in connection with the extremely sound and satisfactory 
generalizations concerning the conservative character of the leaf 
trace, to which the English anatomists have contributed so hon- 
orable a share, is entirely in favor of the concentric as the primitive 
type of cauline bundle in the fern series. 
It follows that none of the recent work overthrows the generali- 
zations put forward in the writer’s earlier memoirs as to the phy- 
logeny of the stem in the vascular series. It now in fact appears 
much more clearly than formerly that the primitive condition of 
the vascular system in both stem and leaf in the Vasculares as 4 
whole was what the present writer has designated protostelic, 
that is, a condition in which the fibrovascular tissues harbored 
no pith. Following this condition was one in which the fibro- 
vascular system became transformed, especially in the more pro- 
gressive stem, into a stelar tube lined both internally and externally 
with phloem and endodermis. In the process of time the internal 
phloem became degenerate, probably on account both of the absence 
of direct relation to the leaves and of the appearance of secondary 
growth, advantageously localized ultimately on the outer surface 
of the stele. The internal endodermis more slowly followed the: 
internal phloem into oblivion, and is often found at the present 
time in the young individual where it is absent in the adult (Ophio- 
glossaceae, Equisetaceae, Ranunculaceae). The pith must in all 
cases be regarded as a derivative of the cortex, which has become 
more or less completely sequestered within the stele. The tubular 
stele may with propriety and accuracy continue to bear the design@- 
tion siphonostelic, a term moreover which, in addition to having 
