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68 ON THE SKXUAL OllGANS OF THE CYCADACEtE.
already potentially determined. Tlie final result of the formation of
an ovule is the differentiation of one of the cells situated in its axis,
which produces the new individual ; in this vvay the embryo-sac is to a
certain extent the equivalent of the parent-cell of the bud. The em-
bryo-sac is fertilized by the absorption of matter contained in another
cell which places itself in contact with it ; and if we inquire the cause
of the individualization of the parent-cell of a bud, it must be looked
for also in the phenomena of nutrition, of which the adjacent parts are
the seat. Modifications of the movements and distribution of the nu-
tritive juices are the means of exciting the production of buds. The
destruction of a terminal bud causes the production of numerous lateral
ones. Incisions, by accumulating the supply of food at particular
points (of a leaf or root, for example) cause the production of buds
there. The ovule is usually considered as distinct from the carpel, and
the line of separation drawn at the origin of the funicle ; but would it
not be more philosophical to regard it as a stage in the development
of a particular part of the carpel, and to look upon the embryo-sac
alone as a new and independent structure ?
The search amongst monstrous structures for the key to the true
meaning of the parts of the ovide is a proceeding which encounters
serious difficulties in the circumstance that the parts are very frequently
so altered in position and form as to be scarcely recognizable with suf-
ficient certainty. The normal organogeny of carpels and ovides, which
has been chiefly studied in Angiosperras, supplies good information as
to the external aspects of the phenomenon, and reveals to the eye its
anatomical characters, but it will always be extremely difficult to pene-
trate in this way into the morphological interpretation of organs re-
duced to their minimum of development. Besides this, the complete
history of the evolution of the leaf is still wanting ; even after the
a(bniral)le researches of Eichler, it has not been distinctly ascertained
in all its bearings. Und^r these circumstances the consideration of
the carpopliylls of the Cycddacem, which are less modified by metamor-
phosis than the corresponding organs in all other Phanerogams, Avill
perhaps supply some explanation as soon as their development has
been completely studied,—a labour for which unhappily the materials
cannot be obtained, except in the native country of the plants.
I have consequently confined myself to calling attention to the fol-
lowing points :
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