250 Bower . — Imperfect Sporangia in certain 
In seeking to understand the nature of the protophylls it 
is a material fact that they are not sharply marked off from 
the typical foliage leaves: in embryos, of the cernuum type 
they merge gradually into the normal leaves, which in their 
turn pass on into sporophylls. And even in Pkylloglossum, 
where usually the distinction is more marked, intermediate 
steps have been seen between the protophyll and the sporo- 
phyll. Another fact of importance is that protophylls are 
absent from some Lycopod embryos, and when present 
are only found on the protocorm. The relation of these 
parts, the protophyll and the protocorm, are evidently close ; 
and as the protocorm may, on my view, be regarded as a 
special turgid development of the lower part of the stock, so 
the protophylls may be regarded as turgid types of leaf, the 
transitional forms to the normal foliage giving some idea of 
the steps of their specialization. 
In the Lycopodineae we have thus three categories of leaf 
which merge into one another. We have seen that in the 
Selago type the sporophylls do not differ from the foliage 
leaves ; that the first leaves of the Selago plantlet are normal 
foliage leaves ; and that sporangia may be produced after the 
second branching of the young plant. It does not seem a 
strained interpretation of these facts that in Selago all the 
leaves from the first are potential sporophylls ; but that those 
first formed are usually sterile by complete abortion of spo- 
rangia. We may then conceive the primitive embryo of 
Lycopodium as of the Selago type ; with a hypocotyledonary 
stem which forms the first root near its base ; with no proto- 
corm nor protophylls, nor greatly enlarged foot ; but connected 
by a suspensor and small foot with the prothallus, and its 
origin of such haustorial structures, but the inconstancy in vascular plants at large 
prevents too precise generalization. Dr. Treub, referring to this question (Buit. 
Ann., v, p. 130), remarks that my conclusion goes too far, in denying the morpho- 
logical value of the foot in Vascular Cryptogams. But the further examples since 
described confirm me in the opinion. Goebel (Organographie, ii, p. 450) suggests 
that the term foot should be dropped, and haustorium substituted : this is a colour- 
less term, which does not suggest any morphological identity for the parts included 
under it, but only physiological correspondence. On this ground the suggestion 
may be upheld. 
