248 BOTANICAL GAZETTE [ocroBER 
like those occurring in the reduced Lycopsida, thin serial sections 
are necessary to a proper understanding of the real anatomical 
relations. It may be stated in conclusion that there are no real 
foliar gaps in Tmesipteris and that statements as to their presence 
depend on errors of observation and interpretation. 
In Psilotum leaf-traces are absent in the case of the vegeta- 
tive leaves, but as the angles of the stellate central cylinder sub- 
tend the ridges of the stem from which the leaves take their origin, 
there can be no question of the presence of foliar lacunae in this 
genus. Traces are present in the case of the sporophylls, but as 
these in general occur on the smaller terminal branches, where the 
stele is solid, they do not serve to elucidate the subject. It is of par- 
ticular interest that the leaf-traces should sometimes disappear 
altogether in the case of the small-leaved forms (the Lycopsida). 
The writer has called attention to this condition as occurring in the 
case of the basal foliar sheaths of the smaller branches of Equisetum.” 
EQUISETALES 
It is in regard to the supposed existence of foliar gaps in the equise- 
tal series that the writer has received the most weighty criticism. Dr. 
Scott in his masterly treatment of Paleozoic botany in Progressus 
ret botanicae, adopting the present author’s division of vascular 
plants into two phyla, the Lycopsida and Pteropsida, states that it 1S 
“open to much criticism; the general grouping however has sufficient 
claims to be a natural one, to afford at any rate a basis for the dis- 
cussion of affinities.” The only feature “open to criticism” ated 
which Dr. Scorrt lifts the veil is in regard to the absence of foliar 
gaps in Equisetum. His words are as follows: “The absence of 
foliar gaps, upon which JEFFREY lays stress, may hold good in the 
case of Archeocalamites, but if I rightly interpret the structure, ee 
are present in the Calamariaceae as well as in the recent genus. 
It will be the writer’s task to show that not only are foliar gaps absent 
in the older genera of the Equisetales, but that they also do not occur 
in the living genus Equisetum. 
. D 
Professor CAMPBELL’s criticism of the present writer’s work 0 
; ist. 
*« Structure, development, and affinities of Equisetum. Boston Soc- Nat. His 
Memoirs 5: no. 5. p. 176. 
