1914] THOMSON—SPUR SHOOT 383 
This is certainly a very branchlike feature, and it is noteworthy 
that it occurs in the most ancient spur shoot-bearing conifer on 
record. 
The paleontological evidence afforded by the fossil pines sup- 
plements that from the living forms, and makes the case for the 
specialized character of the spur shoot of the pines practically 
complete. The spur then, as it stands today, is only a specialized 
branch which is of limited (primary and secondary) growth and 
bears a limited number of specialized and cyclically arranged leaves; 
whereas its progenitor, judging from the adult living and fossil 
forms and from the seedling and traumatic phenomena above 
described, was an ordinary branch. If such is the case, the genus 
Pinus is a specialized one in respect to its fascicled foliage, and the 
spur shoot of the pines cannot be the indication of primitiveness 
which JerrrEy’s statement, quoted in the introductory paragraph, 
would lead us to expect. According to it, the fascicled condition 
of the leaves is “a primitive attribute of the coniferous stock.” 
This condition, he considers, has been retained in the cone of all, 
but “in the vegetative parts of only the very ancient genus Pinus.” 
It is not apparent why Pinus is singled out for this distinction and 
not some of the other spur shoot-bearing conifers, or Sciadopitys 
whose cladode is recognized by all adherents to the “brachyblast”’ 
theory of the cone structure as the closest approximation in the 
vegetative parts to the condition in the cone scale. Moreover, 
JEFFREY, in stating the arguments in support of his view, puts much 
emphasis on the homology of the cone structure of the living and 
cordaitean forms (13, p. 23). The latter, he, incommon with many 
other anatomists, regards as the ancestors of the conifers. If 
JEFFREY’s inference that fascicled leaves are ancestral for the coni- 
fers because of the brachyblast structure of the cone, be applied 
to the cordaitean forms the logical conclusion is that they must 
have had their leaves in fascicles. Of this there is not a vestige 
of evidence. All that the “brachyblast”’ theory postulates in this 
regard is the power of branching, a feature which is common to 
both Cordaitales and Coniferales. If, moreover, the spur is “a 
Primitive attribute of the coniferous stock,” we should expect 
Some indication of this in the primitive regions of the non-fascicled 
conifers; in their seedling, on their fruiting branches, as a result of 
