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ON THE SEXUAL ORGANS OF THE CYCADACER, 75 
which therefore performs the function of a stigma, is entirely naked, 
and secretes a viscous fluid. After a short period, the internal capacit 
of the cone is entirely filled with cellular tissue, which afterwards 
softens, and is partially reabsorbed. Mucilaginous channels (the paths 
taken by the pollen-tubes) are formed in it, which terminate below the 
wall of the embryo sac, in what have been called the areole, beneath 
which are situated the opercular rosettes of the corpuscles. (Plate XCI. 
fig. 12, 10 and 11, a section of the free summit in the direction of its 
length.) The upper wall of the embryo-sac being situated at the level 
where the nucleus becomes free, and where the base of the cone is 
solidly united to the coat, the cone.is anatomically separate from the - 
adherent portion of the nucleus, and as that becomes forced outwards 
and compressed by the dilatation of the endospermic cavity, this trans- 
verse separation becomes more and more distinct. Finally it withers, 
and it is afterwards found, particularly in fertilized fruits, applied as a 
cap on the top of the endosperm. In this condition it formerly re- 
ceived from some authors the very inexact names of vitellus or scutel- 
lum. (Plate XCI. fig. 13 a, Plate XCII. fig. 11.) 
The history of the embryo-sac or amnios is very complicated, and it 
was not til after Hofmeister, Pineau (Annales des Sciences Nat., 
-3me série, ii, p. 83), and others had unravelled it in the Conifere, that 
I found it intelligible amongst the Cycadacee. The exact time of the 
first appearance of the embryo-sac I do not know, but it is quite certain 
that it takes place at a very early period in the existence of the ovule, 
and in the upper half of the adherent portion of the nucleus, termed 
2 Hooker the corpus nuclei. From its first appearance, the cavity of 
e embryo-sac is filled with cells. At this period it is small and 
BEBE and its wall may be seen to consist of simple cellular mem- 
brane. I have only twice had the opportunity of examining it in this 
state, once in a Cycas, and once in a Zamia. The interior cellular 
tissue next disappears, and the cavity enlarges, and becomes filled with 
a mucilaginous fluid; from analogy with what takes place among 
Conifere, oue would be led to believe that the period of fecundation 
approaches at this point. The second stage now commences, and 
as it is also completed in unfertilized ovules (fertilized ones have 
not yet been observed in botanie gardens), there is no reason for 
doubting that it is independent of fertilization. The free and rapid 
development of cells produces a highly developed albumino-plastic 
