the extravagant hypothesis of M. Fillette de Clermont, who fancies that it is due to the cohesion of 3 flowers." — Lindley's Natural System of Botany.
"This genus only differs from the other Myrtaceae by having two verticels of carpels developed instead of one, and perhaps in a truly wild state the upper or adventitious one may occasionally disappear. The inner series (or those at the bottom of the fruit) have their placentæ in the axis ; but the outer series, forced to the top of the fruit by the contraction of the mouth of the tube of the calyx, having their placentæ in the ovary at the back of the inner carpels, exhibit them in the ripe fruit in a horizontal position on the upper surface of the lower cells." — Arnott Encyclop. Brit. Ed. 7, et Prod. Fl. peninsula I Pg. 327.
Premising that the whole controversy turns on these questions, 1st, what is the true structure of a Pomegranate? and 2d, whether the difference between it and Myrtus is sufficient to separate these genera as types of distinct orders ?
I shall now proceed to examine these conflicting statements and endeavour to ascertain on which side the balance preponderates and whether indeed, there is not room for an explanation different from any of these yet proposed.
Mr. Don's description of this fruit on the strength of which he first proposed to remove this genus from Myrtaceae, the order with which it was previously associated, as a distinct family appears to me most unphilosophical and altogether, untenable. He, as I understand, considers the fruit a one celled receptacle the centre of which is filled with a spongy placenta, round the surface of which there are a number of irregular cells occupied by clusters of ovules: but he does not tell us how the central placenta got there neither does he account for the ovules being attached to the parietes of the cell and not to the central placentæ.
His whole description in fact proves that it had been drawn up from inadequate examination and that he, at the very time he is accusing all authors of overlooking the real structure of this fruit, totally misapprehends it himself, as we shall by and by see.
DeCandolle gives a more correct description of it when he says that it consists of two chambers, the under 3-celled, the upper from 5 to 9-celled, with the placentas of the upper cells reaching from the parietes to the centre while those of the lower division proceed irregularly from the bottom of the fruit. He does not however assign this peculiar structure as his principal reason for viewing the order as distinct from Myrtaceae, but has recourse to others in my estimation of minor importance.
Lindley conceives that there are two rows of carpels, three or four of which surround the axis at the bottom, while the remainder surround these and occupying the upper part of the fruit adhere to that part of the tube of the calyx. The placentas of these upper carpels he conceives contract an irregular kind of adhesion with the back and front of their cells. The meaning of this is far from being: clear to me, but if it means that he considers the placentas of the upper as well as the lower row to proceed from the axis towards the circumference to which last they contract accidental adhesions, then he takes an erroneous view and if the examples quoted in illustration support this view, they are not in point as regards the structure of Punica.
Mr. Arnott like Lindley views the fruit as consisting of two rows of carpels, an outer and inner, the former of which he thinks may be adventitious. To understand his theory we must first suppose the tube of the calyx spread out as a flat surface and covered with two circles of carpels, the inner next, the axis and the outer occupying a larger circle beyond. That the margin of the calyx then contracts so as to turn the outer series over the inner. According to this supposition, the attachment or base of the placentas of the outer series should be in the circumference and the apex in the centre, while that of the inner should be in the opposite direction, that is, have the base in the centre and the apex towards the circumference, an explanation which is in accordance with what we find, except in so far as it does not account for the horizontal partition between the two series, nor can I exactly understand on what ground we are warranted in assuming that the outer series is adventitious and the result of cultivation, as it has every where been found so constant in all circumstances. But be that as it may. this theory certainly accounts for the crossing of the placentas in the two rows, which we so invariably find, whether correctly or not cannot be determined until we get fruit with a single row of carpels, which has not yet been found.
