ON THE PR0TEACE.E OF JUSSIEU. 23
chalaza, which, whatever may be the point of insertion of the seed, is always situated at its upper extremity ; and I have not been able to observe any fasciculus of vessels connecting it with the umbilicus in cases where this latter is placed in a different part of the seed.
I am not aware of any function being ascribed to the chalaza of seeds, except the nutrition of their proper membrane : but it appears to me too remarkable a part to be destined for this purpose only ; and some observations I have made induce me to suppose that it is the organ [36 secreting the liquor amnios. This opinion I was first led to form by observing in some species of Persoonia, in which the inspissated remains of this fluid are visible in the ripe fruit, that it evidently originated in the chalaza and con- tinued to adhere to it : nothing has hitherto occurred to invalidate this opinion, which is here however hazarded merely as a conjecture, requiring for its confirmation more numerous and decisive facts than I can at present adduce.
That the albumen of seeds is merely that condensed portion of the liquor amnios which remains unabsorbed by the embryo, seems to me very satisfactorily established ; and as this fluid is in the early stage never wanting, all seeds may in one sense be said to have albumen : but while in some tribes this unabsorbed part in the ripe seed many times exceeds the size of the embryo, so there are others in which not a vestige of it remains ; and such has hitherto been supposed to be the case with Proteacege : nor are the few exceptions with which I am at present acquainted of so decisive a nature as to invalidate this cha- racter of the order ; for they occur only in some species of Persoonia, where the semi-fluid remains of this substance are observable between the cotyledons ; and in Bellendena, in which it continues to form a thin fleshy coat on the inner surface of the proper membrane of the seed. From such instances, however, we may expect to find plants with a more copious albumen, which nevertheless it may be necessary from the whole of their organisation to refer to this family.
The radicula pointing towards the base of the fruit in
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