IN THE CLUSIACEA, MAGNOLIACEÆ, ETC. 91 
centres, and thus formed one complete tunic, which finally assumed the solidity and 
texture of a crustaceous shell, which he called a * false testa”: this again became 
enveloped by a second placentary extension, in the form of a transparent soft pulp. 
These facts had been previously authenticated by the careful observations of Gasparini*, 
who describes, with great apparent accuracy, the curious phænomena attendant on the 
growth of the ovule of Opuntia, from its earliest development to the state of its ripe 
seed. After its anatropal inversion, the ovule is seen suspended by its short funicular 
cord (podosperm) from the hilum, which cord, in form of a placentary sheath, or thick 
cylindrical filament, is seen to extend itself round it, until it encircles the ovule like an 
annular ring: from this ring, on each side, a distinct membrane, at first very thin, 
expands itself by slow degrees, until at length, on both sides, it becomes extended in a 
complete tunie, over the entire surface of the ovary. After the period of fecundation, he 
farther observes, if we watch every now and then the growth of the ovary, during its 
transformation to the state of seed, we see the tunic just mentioned, as well as its very 
short podosperm, become covered, little by little, with a pulp. In proof of the fact that 
the production of this more external tunic originates in the extension of the podosperm, 
he states that sometimes, in some ovules, from some unknown cause, the above-described 
annular prolongation of the placentary sheath is not formed, and in such case the seed is 
not covered with the usual pulpy envelope. Some explanation, however, is here requisite, 
which I am enabled to give from the examination of the large seed of a species of Opuntia, 
collected by me in Chili many years ago. This has convinced me of the correctness of 
the details given by Gasparini and Planchon, with this exception, that the thin pellicular 
membrane, which both actually witnessed in the act of its growth and extension over the 
primine, and which the latter imagined became converted into the thick osseous shell, 
is no other than the intermediate epidermoid tunic, which I found still covering the 
Shell. We may feel assured that the deposition seen of osseous cells, to form the 
crustaceous shell, took place in the substance of the primine, and not in its arillinar 
covering, as Dr. Planchon inferred, for Gasparini makes no mention of such aD-ooour 
rence. That suchis the case, is manifest from the position of the raphe, and it is not less 
| clear, from the phænomena observed, that the membrane, as they saw it in the progress of 
its growth, is a production of the placentary sheath, and is therefore of the nature E "- 
arilline. So, in like manner, the pulpy envelope emanates from the placentary sheat rn 
funicle ; and that such is really its origin is proved by the curious fact related by — 
that when, as it sometimes happens, the placentary sheath is unformed, or grue 
pulpy matter takes place over the seed. From the circumstances above peas = 2 
safely conclude that the hard crustaceous shell in the seed of Opuntia = sr sd å 
its annular ring is the raphe, and that the intermediate tunic coating e sip 
arilline; while the more exterior pulpy envelope, whether originating in the p Ty 
sheath or the funicle, is still an aril, because it is void of spiral vessels. = 
Another striking confirmation of the fact of the gradual increment of the fles A 
over the primine, is eited by Dr. Planchon, and is the more important, because i 
occurs in Clusia, and bears immediately on the question at issue. Je de before 
* Osservazioni intorno alla struttura dell’ arillo. Rendiconto dell’ Accad. delle — T ga ^ er 
