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Igto} JEFFREY—PTEROPSIDA 411 
the application of sound logic to the known facts, that the pith 
in these families or orders is morphologically included fundamental 
tissue. 
On the basis of conclusions drawn from the leaf trace in existing 
; _pteridophytic groups, we must regard the concentric as the primi- 
tive type of fibrovascular bundle. This view of the matter is 
_ strengthened by the fact that the concentric bundle is character- 
istic of the phylogenetically older representatives of the Pteropsida. 
In the case of the Lycopsida, unfortunately, the evidence is very 
defective, since this phylum reached its culmination in the remote 
_ past and is now almost extinct. The English view of the matter 
is diametrically opposite, namely, that the collateral bundle is 
more ancient and that the concentric type has been derived from 
it. It has been cited in favor of this view, originally by Dr. Scorr 
and afterward by nearly all the younger English anatomists, that 
_ ho evidence is forthcoming in favor of the superior age of the con- 
centric type of bundle in the case of the seedling of the ferns which 
have collateral stem bundles in the adult. This statement appears 
to be entirely fallacious. In the first place it would be just as 
reasonable to assume that centripetal or cryptogamic xylem was 
not originally present in the stem bundles of our existing gymno- 
sperms, because forsooth it has never been found in the seedling stem. 
The present writer entirely agrees with the English anatomists 
in the conviction that centripetal xylem was once well developed 
in the stem of the ancestors of the living gymnosperms, but this 
conclusion rests on the persistence of this type of xylem in the 
leaf trace of forms actually living or their immediate ancestors. 
On the same basis of argument, concentric bundles were originally 
Present in the stems of those few ferns which today show a col- 
lateral condition in their cauline system, for here, as in the gym- 
hosperms, the structure of the leaf affords evidence which is no 
longer supplied by the seedling. Moreover, if the collateral type 
of bundle is really primitive for the fern series as a whole, one 
would expect to find some evidence of its presence in the seedlings 
of the extremely numerous modern ferns which are characterized 
- by the presence of concentric bundles both in their stems and 
leaves. Although a great deal of attention has been devoted by 
