242 BOTANICAL GAZETTE [OCTOBER 
the hypothesis, as might be expected, have been raised by those 
whose published views are prejudicially affected by its validity. In 
spite of all that has been written on the subject, however, the author 
has seen no reason to modify his standpoint in any essential feature. 
It is proposed in the present article to deal with some of the objec- 
tions, mainly resulting from a misapprehension of the author’s state- 
ments or an unfamiliarity with the anatomical field, which have been 
raised against the Lycopsida. In a subsequent article the Pteropsida 
will receive consideration. 
It will perhaps be well at the beginning to define the Lycopsida 
and Pteropsida in a comprehensive way and to include external 
characters as well as anatomical ones. 
LycopsipA.—Palingenetically microphyllous vascular plants, with 
ventrisporangiate sporophylls (sporangia adaxial), the tubular central 
cylinder when present characterized by the entire absence of gaps OF 
interruptions in the fibrovascular tissue immediately above the out- 
going leaf-traces——Lycopodiales, Psilotales, Equisetales, Spheno- 
phyllales. 
PTEROPSIDA.—Palingenetically megaphyllous vascular plants, with 
dorsisporangiate sporophylls (sporangia abaxial), the tubular central 
cylinder when present characterized by foliar gaps or interruptions 
in the fibrovascular tissues immediately above the outgoing foliar 
traces.—Filicales, Gymnospermae, Angiospermae. ; 
It is necessary to define very clearly, on account of numerous mis- 
conceptions and misunderstandings, the nature of a foliar gap, for the 
writer’s critics have shown considerable versatility of misunder- 
standing in regard to this important feature. In one of the more 
simply organized ferns (Ophioglossum, Osmunda, Schizaea, ea 
Adiantum, etc.), wherever a leaf passes off from the surface of the 
stem, it carries with it a fibrovascular strand, the leaf-trace- : 
foliar trace is derived from the tubular central cylinder of the ste™, 
and as it bends away from the surface of the stele in its outw er 
upward course, it causes immediately above it, in the stelar W2" 
interruption of the fibrovascular tissues, known as the Teaf fi 
The foliar gap may be distinguished from other gaps in the rr 
the fibrovascular hollow cylinder by the fact that it ene 
diately above a leaf-trace. A true foliar gap, moreover,  ‘ 
