Sir obi lies in A rchegonicite Plants. 363 
vascular plants, I should rather regard them as later deri- 
vative forms, characterized by an extravagant growth of the 
leaf and its appendages. 
The chief points which the Ferns have in common with 
the Ophioglossaceae are the large, often compound leaf, and 
numerous, often separate, sporangia. It is easy to imagine 
the origin of these two families by parallel development from 
a smaller-leaved ancestry : in the one case the extension and 
septation of a definite sporangium of Lycopodinous type 
would result in the so-called fertile frond of the Ophio- 
glossaceae, this enlarging separately from the subtending leaf : 
in the other the spore-producing body would throughout be 
closely connected with the enlarging leaf-surface and be spread 
out over it, as we see to be the case in Danaea. The method 
of advance in complexity would be virtually the same in both 
cases, viz. by septation, and subsequent separation of the 
several sporangia. But evidence on such points as these is 
but of the slenderest. 
If this theory be applicable to the strobilus of Vascular 
Cryptogams, it should also be so to the flower of Phanero- 
gams. At present I do not propose to pursue the matter 
further in this direction, beyond saying that I see no valid 
objection in the way, while the recognition of the Phanero- 
gamic flower as a strobilus of ultimate origin like that of 
Vascular Cryptogams would make certain difficulties of floral 
morphology appear less serious. But though the Phanero- 
gamic flower be accepted as the homologue of the strobilus, it 
must never be forgotten that while the homosporous strobili 
are entirely non-sexual, the flower of Angiosperms is in its 
development intimately connected with the sexual function. 
The presence of this important factor in the one, and its 
absence in the other makes it difficult to draw physiological 
comparisons between them as regards the conditions which 
would produce or modify them. 
In previous attempts to explain the origin of the complex 
strobilus of vascular plants, some idea of terminal branching 
similar to that branching which is occasionally seen in abnormal 
