108 THE SPORANGIUM DEFINED 
he approves of the method by which it is arrived at: that is, the method 
of recognition of the archesporium by “a last analysis” of cell-origin. 
Secondly, Goebel’s method of recognition of the archesporium is not 
consistent: he designates the inner product of the hypodermal layer in 
the Angiospermic stamen the archesporium, notwithstanding that the 
“schichtzellen” and the tapetum are sister-cells with it. But in the 
Pteridophyta, on the ground of common origin by segmentation, not only 
the tapetum but also the sporangial wall itself are described as derived 
from a superficial archesporium. If the recognition of an archesporium 
is to be based upon ‘“‘a last analysis” of the segmentations, then the 
hypodermal layer of the Angiospermic anther, and not merely the inner 
product of its segmentation, is the archesporium. 
Thirdly, the recognition of the archesporium by the method of “a 
last analysis” brings together under a common head, merely on the ground 
of early segmentations, things which are not really comparable, and ascribes 
a distinct origin to things which are indistinguishable when mature. The 
superficial archesporium of the Pteridophytes gives rise to part of the 
sporangial wall and of the tapetum: the archesporium of the Angiospermic 
anther, on Goebel’s definition, gives rise to neither. It is impossible to 
conceive how by any known evolutionary progression the former type of 
“archesporium ” could pass into the other, and the superficial cells be covered 
over: therefore the two are to be regarded as not truly comparable. Further, 
the recognition of superficial cells in the Pteridophytes as archesporial 
draws a distinction between part of the sporangial wall which originates 
from them, and the rest which does not: thus in the Leptosporangiate 
Ferns the apical part of the annulus would be archesporial, the lateral 
parts would not. 
With all respect to the opinion of the writer who introduced the term, 
I think that this Jast change in its application, as suggested by Wilson 
Smith and accepted by Goebel, makes more obscure the meaning of a 
word which never has been clear. The Bryophyta provide a vreductio ad 
absurdum of the method of “a last analysis”; for, following this method, 
in Sphagnum and some others the amphithecium would be reckoned as 
the archesporium, while in the ordinary Bryineae it would be the 
endothecium: or, carrying the analysis in the latter case to its extreme 
limit, the first segments in the upper half of the zygote, or even the 
ovum itself, would be the archesporium. 
The fact is that this sort of analysis of formative tissues has served 
its turn: it has led to much detailed investigation, which has, however, 
shown that the segmentations which lead up to the formation of spore- 
mother-cells are not comparable in all cases. The time has come, in 
presence of many divergent details, to admit frankly that there is no 
general law of segmentation underlying the existence of that cell or cells 
which “a last analysis” may mark out as the “archesporium,” and _ that 
therefore the general application of such a term to those cells which the 
