| 36 | Mr. Brown, on the Proteaceae of Jussieu. |
me to suppose that it is the organ 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 originate in the chalaza and continued 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 Proteaceæ: nor are the few exceptions with which I am at present acquainted of so decisive a nature as to invalidate this character 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 maybe necessary from the whole of their organization to refer to this family.
The radicula pointing towards the base of the fruit in all Proteaceæ is a circumstance of the greatest importance in distinguishing the order from the most nearly related tribes; and its constancy is more remarkable, as it is not accompanied by the usual position or even uniformity in the situation of the external umbilicus.
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