66 ON THE SEXUAL ORGANS OF THE CYCADACEA. 
phylls (and also in many points the androphylls *) are composed of 
the same kinds of tissue as the leaves. Vascular bundles leaving the 
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 lamiuz 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, Macrozamia, Encephalartos, 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. 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 the 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 with great clear- 
ness by Braun (‘ Polyembryonie und Keimung von Celodogyne,’ 1860, 
p- 186). Braun himself was inclined to think that the coats might 
be regarded as developments from the funicle. Caspary (** Vergrünun- 
gen der Blüthe des Weisklees:" Physik. (Econ. Gesellsch. zu Königs- 
berg, 2nd year) raised objections against his view, as well as against 
It is convenient to adopt this term instead of an expression like Lindley's 
* 
* antheriferous cone-scales.”—W. T. D. 
I use the expression vascular bundles for iis are — the equivalents of 
udis composed of true vessels, for among the Cycads, as well as in vascular 
Cryptogams, only vascular cells, closed at the itid occur in the bundles. 
Among these cells, ara , netted, scalariform, and porous varieties occur in 
Cyeads. (On this low be ig of vascular bundles see Caspary, « Ueber die @efäss- 
bündel der Pflanzen the ‘ Monatsberichte der Berliner Akademie der 
Wissenschaften,’ cdd 10, 1862.) 
