Osmunda claytoniana , Z., <2;^ O. cinnamomea , L. 87 
a careful study of the development of the prothallium shows 
so many points of resemblance to that of the Filicineae, that 
a distinct relationship, remote it is true, is hardly to be 
questioned. The early stages of the prothallium, develop- 
ment of the sexual organs, structure and development of the 
spermatozoids, and early divisions of the embryo — all of these 
correspond closely with the Filicineae, especially Osmunda. 
Whether they correspond equally with the same points in the 
Ophioglosseae, where the nearest affinities would be looked 
for, remains to be seen. The latest researches of Buchtien \ 
show quite close resemblances, too, in the growth of the female 
prothallium, which are, however, disguised by the formation 
of lobes, at the base of which the archegonia are formed, and 
the subsequent shifting of the archegonia to the upper surface 
of the prothallium, although they are originally formed upon 
the lower side. 
VanTieghem has also called attention to certain resemblances 
in the sporophytes of Equisetum and Ophioglossum , and it is 
highly probable that when the embryogeny of the latter is 
known that the resemblances will be still more marked. 
It is well known that in Equisetum the fibro-vascular bundles 
are collateral, while in most of the Filicineae they are con- 
centric ; but in Ophioglossum the bundles are collateral, and 
this is true of the stem, at least, in Botrychium and Osmunda ; 
and as we have seen, a trace of this structure is visible in the 
bundle of the petioles of the cotyledon of Osmunda , as well as 
the smaller veins of the leaves of the ferns. 
Just as the primitive type of sporangium derived from the 
eusporangiate ferns has persisted in the Spermaphytes, so we 
may assume has the collateral fibro-vascular bundle ; and the 
concentric bundle, characterizing the more specialized ferns, 
is a derivative of this. Really the two forms are not very 
different, and may merge almost insensibly into each other, 
as is clearly shown by comparing the bundles in the petiole of 
different species of Botrychium. 
The impossibility of making a fair estimate of the relation- 
1 L. c. p. 23. 
