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66 ON THE SILXL'AL ORGANS OF THE CYCADACE^.
pliylls (and .nlso in many points the andropliylls *) are composed of
the same kinds of tissue as the leaves, Avascular bundles leaving tlie
stem penetrate them in a semicircle, and following their longitudinal
axis, pass parallel to one another through the petiole and midrib, curve
outwards towards the segments of the barren laminae in Cycas, and
traverse each segment without dividing, exactly as they are distributed
in the leaflets of the ordinary leaves. They turn in just the same way
towards the point of insertion of the ovules into which they penetrate
(Plate XCI. fig. 1. C. revoluta). An analogous arrangement of bundles,
parallel in the petioles, and diverging at the upper part, occurs in the
carpophylls of Dion, Maci-ozaniia, E)icephalartos, and Zamia ; only in
consequence of the contraction of the upper parts, and their conversion
into large plates or shields, the bundles take a direction more curved,
and are usually less developed. In all these genera the bundles which
penetrate the ovules may be seen very distinctly.f More or less
cylindrical in a transverse section, they exhibit at the exterior or pos-
terior side a layer of liber-cells, on the opposite side woody tissue.
Laticiferous canals are regularly distributed, and traverse the tissues
just as in the leaves. Chlorophyll cells exist uniformly in the external
layers of parenchyma when young. The epidermis presents no essen-
tial distinction, and tlie stomata which are deeply situated and have
the appearance of little holes, are easily distinguished.
The morphological interpretation of the component parts of the ovule
is not yet completely made out. Botany does not possess as yet any
theory of the ovule which is generally adopted. The attempts which
have been made to frame one, have been summed up Avith great clear-
ness by Eraun (' Polyembryonie und Keimung von Ccelohocjyne^ 1860,
p. 186). Braun himself was inclined to think that the coats might
be regarded as developments from the funiclc. Caspary (" Vergriinun-
gen der Bliithe des Weisklees :" Physik. (Econ. Gesellsch. zu Konigs-
bcrg, 2nd year) raised objiections against his view, as well as against
* It is convenient to adopt this term instead of an expression like Lindley's
" antlicriferous cone-scales."— W. T. ]).
f
1 use the expression vascular bundles for vvliat are only the equivalents of
bundles composed of true vessels, for anions; the Cy