VOLUME XLVI NUMBER 4 
DOTANICAL (a 
OCTOBER 1908 
ARE THERE FOLIAR GAPS IN THE LYCOPSIDA ?* 
EDWARD C. JEFFREY 
(WITH PLATES XVII AND XVIII) 
Six years ago the pzesent writer published an account of his 
studies on the stem of the pteridophytes and gymnosperms.? In the 
Conclusions not only these large groups were considered, but also the 
remaining vascular plants, which had been the subject of earlier 
investigations. The general result was reached “that there are two 
phylogenetic types of tubular central cylinder, namely, that in which 
only ramular gaps are present, and that in which both ramular and 
foliar gaps occur.” Further it’ was stated: ‘‘ The use of these con- 
stant and characteristic anatomical features results in the division of 
the Vasculares into two great primitive stocks—the Lycopsida, which 
= cladosiphonic and palingenetically microphyllous, and the Pterop- 
sida, which are phyllosiphonic and palingenetically megaphyllous. 
The Lycopsida include the Lycopodiales and Equisetales. The 
Pteropsida include the F ilicales, Gymnospermae, and Angiospermae.” 
he opinion was expressed that the Lycopsida and Pteropsida “appear 
to have been separate back to the beginning of the period when 
the paleontological record begins.” Since the publication of that 
memoir, the writer has been busily engaged in other directions, and 
his time has been fully taken up. In the interval a great deal of 
literature has appeared, especially in European countries, on the 
anatomy and phylogeny of vascular plants, and not unnaturally the 
emiter’s hypothesis has been subjected to the criticism which is the 
fate of every scientific hypothesis. The most vigorous objections to 
: ie from the Phanerogamic Laboratories of Harvard University, 
* Phil. Trans, Roy. Soc. London B. 195:119-146. 1902. 
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