On Medullation in the Pteridophyta. 
BY 
F. O. BOWER, Sc.D., F.R.S. 
Regius Professor of Botany in the University of Glasgow. 
With Plate XLVII. 
I WOULD willingly have left the facts and reasoning detailed in the 
preceding paper to take their place without further remarks in the 
general sum of evidence, now so rapidly growing, which relates to the origin 
of the pith in Vascular Plants. And I should certainly have done so, had 
it not been that in a recent number of the Botanical Gazette (Dec., 1910, 
p. 401) Professor Jeffrey has restated his position on this question with 
increasing decisiveness. He first enunciated his views on stelar morphology 
at the meeting of the British Association in Toronto, in 1897. Speaking 
on the original paper, I then pointed out that, in my view, a fundamental 
fallacy underlay the whole of his statement, and that the fallacy arose from 
assuming that all Vascular Plants developed their tissues along the same 
lines. Dr. Scott, in reviewing Professor Jeffrey’s three memoirs, in which 
his theory had subsequently been developed, wrote later in almost equiva¬ 
lent terms. 1 He remarked that ‘ The impartial critic will probably take 
the view that similar vascular structures have originated in different ways 
in various lines of descent, and that no one rigid scheme can be applied to 
all \ Now, after the lapse of thirteen years, Professor Jeffrey still maintains 
a rigid scheme, and as regards medullation affirms for Vascular Plants that 
‘ the pith must in all cases be regarded as a derivation of the cortex, which 
has become more or less completely sequestered within the stele’. 2 In his 
summary he adds a saving clause, stating that ‘ the pith of the Vasculares, 
in all cases where definite evidence is available, is an inclusion of the 
fundamental tissues of the cortex on the part of the stele ’. 
In the years that have elapsed since 1897 I have seen no reason to alter 
my first opinion as to the invalidity of the views of Professor Jeffrey on 
stelar morphology, and especially on the origin of pith. But as the grounds 
for my dissent were not put into print at the time of his first statement, the 
present seems a suitable occasion for doing so, while certain facts will be 
added which bear upon the question. Primarily my objection is the out- 
1 New Phytologist, i, p. 212. 2 Bot. Gaz., Dec., 1910, p. 412. 
[Annals of Botany, Yol. XXV. No. XCIX. July, 1911,] 
