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ON THE SEXUAL ORGANS OF THE CYCADACE;F. 74 
hesion exists with the amniotic membrane). At this point a total 
absorption of the membranes probably takes place, so that the pollen- 
tube can penetrate to the top of the corpuscles. 
The unfertilized corpuscles at this time appear entirely filled with 
cellular tissue, or with a mass of protoplasm regularly divided by 
vacuoles. With respect to this I do not feel quite certain, but when 
the membrane is torn the included mass has pretty much the appear- 
ance represented in Plate } . fig. 5. Ihave found the same state 
in fertilized seeds which possess a normal embryo. It is probable that 
all the corpuscles which exhibit it (Plate XCII. fig. 4) have remained 
unfertilized ; for I have always met with one or two at the same time, in 
whieh a small group of larger cells, from which the suspensor originates, 
could be observed free in the middle of the cavity. I imagine that 
this group at first occupies the base of the cavity, and that it is 
not till afterwards that it is elevated to a higher level by the pressure 
of the suspensor. It may be that this displacement has been simply 
the effect of the preparation which the object has undergone. The 
membrane of the corpuscles is relatively dense and resisting, and by 
transmitted light it seems composed of small cells with thick walls 
(Plate XCII. fig. 2 a, fig. 6, very much enlarged). I formerly stated 
that this was actually the case (Ann. des Sc. Nat. l.c. p. 198), and 
Gottsche held the same view (Bot. Zeit. 1845, p. 400), but we have 
really here what Schleiden has observed in the corpuscles of the Coni- 
ere. The external surface of the cellular membrane of the corpuscle 
is covered in its whole extent with a layer of very small eells, forming 
a kind of epithelium (Hofmeister, Vergleichende Untersuch. pl. 28 
and 29). Gottsche has found the total thickness of the wall in Ma- 
crozamia to be 001 mm. In ripe seeds the corpuscles are situated in 
the upper part of the endosperm. They may be more or less flattened, 
sometimes free above, at other times attached to the lower surface of 
the areola. When the top of the nucleus or dried cone is torn off, 
the corpuscles usually follow with it, with the suspensors coiled up- 
wards by the embryo. I have not been able to ascertain if the cor- 
puscles are perforated at the summit. In those which I look upon as 
unfertilized, not a trace of opening can be seen. In those which have 
been fertilized, the fragments of cells which have been already spoken 
of (Plate XCII. fig. 8) are seen at the extremities. It is possible that 
amongst these débris a passage exists for the pollen-tubes. I have, 
VOL. Vil. [MARCH 1, 1869.] G 
