Robert Brown

“ In these, the nucleus of the seed is not properly a monocotyledonous embryo, but has an appearance and economy more nearly resembling those of the tuber of a root; for, instead of being distinguishable into a cotyledon, a plumula and radicula, and of germinating in a determinate manner and from a single point, it is composed of a mass whose internal structure is uniform, and on the surface of which frequently more than one germinating point is observable. ”

“ In the instances of naked seeds now given, the bursting of the pericarpium precedes the distinct formation of the embryo, while the proper coats of the seed remain entire till after its separation from the parent plant, and germination has commenced.
It may not be uninteresting to contrast this economy with that of the Mangroves and other plants of tropical countries, which grow on the shores, and within the influence of the tide. In many of these the embryo, long before the seed loses its original attachment, acquires a very considerable size ”

“ For if we suppose, as the immediate effect of impregnation, a swelling of the ovulum without a corresponding enlargement of the ovarium, the consequence will obviously be a premature rupture of the ovarium, and the production of a seed provided with its proper integuments only. ”

“ Another example of this early and regular dehiscence occurs in an undescribed genus of the same family, which differs from Sterculia platanifolia in its pericarpium having a terminal wing and a single seed.
In the specimens of a plant lately sent from Brazil by Mr. Sellow, I observe a similar economy. In this case the ovarium, which is originally unilocular with five parietal placentæ, soon after fecundation opens regularly into five equal foliaceous valves, to the inner surface of each of which an indefinite number of ovula are attached. ”

“ For, in the first place, its habit is entirely that of the original species of the genus. And secondly, though the pericarpium of Leontice Leontopetalum, which is the type of the genus, remains shut until the ripening of the seeds, and attains a size more than sufficient for the mere purpose of containing them; yet in Leontice altaica, a species in other respects more nearly approaching to L. Leontopetalum than to L. thalictroides, the pericarpium, though it enlarges considerably after impregnation, is ruptured by the seeds long before they have arrived at maturity. ”

“ That such a covering, distinct from the seed, really exists, may in most, perhaps in all, cases be satisfactorily shown by a careful examination of the unimpregnated ovarium, to a part only of whose cavity the ovulum will be found to be attached. ”

“ It is well to remark, however, that his general involucrum is formed of the bracteae subtending and in equal number with the outer partial capitula; and that the general receptacle has no other paleae than the analogous bracteae of the inner capitula. It is the more necessary to take this view of the structure, as I have found in New Holland a nearly related genus (Calocephalus) , which differs from Craspedia and Richea in the want of these bracteae, as well as in the partial receptacles being without paleae;, and in the rays of the pappus being plumose only in the upper part. ”

“ My second objection to M. Cassini's account is, that he describes the nerves as marginal through their whole length. I have formerly, in the passage already quoted, stated them to be parallel and approximated to the margins of the laciniæ. Perhaps in no instance can the branches be considered as strictly marginal; in many cases they are manifestly distinct from the margins, and in the genus Hymenopappus are further removed from them than from the axis of the laciniæ. ”

“ These, as they exist in the whole class and are in great part of it the only vessels observable, may be called primary. In several genera, however, other vessels occur, alternating with the primary, and occupying the axes of the laciniæ: in some cases these secondary vessels being most distinctly visible in the laciniæ, and becoming gradually fainter as they descend the tube, might be regarded as recurrent ”

“ A monopetalous corolla not splitting at the base is necessarily connected with this structure, which seems also peculiarly well adapted to the dense inflorescence of Compositæ; the vessels of the corolla and stamina being united and so disposed as to be least liable to suffer by pressure. ”

“ It may seem rather paradoxical to select Euphorbia as an example of the same relation; this genus being considered by Linneus, and the greater part of the botanists who have adopted his system, as having a dodecandrous hermaphrodite flower. We have already, however, I believee sufficient evidence that this supposed hermaphrodite flower is in reality formed of several monandrous male flowers surrounding a single female [4] . ”

“ As, however, the facts formerly stated appear to me of some importance, and are as yet unpublished, I take the liberty of again submitting them to the Society, along with a few additional instances of anomalies in the structure of seeds and fruits, hardly less remarkable than those contained in the original essay. ”

“ Ferdinand Bauer, will materially assist in explaining the singular economy now described; and may also perhaps render more intelligible the account I proceed to give of the second instance in which I have observed an analogous structure, but to illustrate which I have at present no drawing prepared. ”

“ In H. tenuifolius this irregularity is still greater; one branch being not unfrequently altogether wanting, and even the remaining branch considerably weakened: where this happens a secondary vessel is always produced, though very few flosculi are furnished with five complete middle nerves. ”

“ Page:Transactions of the Linnean Society of London, Volume 12.djvu/128 Page:Transactions of the Linnean Society of London, Volume 12.djvu/129 Page:Transactions of the Linnean Society of London, Volume 12.djvu/130 Page:Transactions of the Linnean Society of London, Volume 12.djvu/131 Page:Transactions of the Linnean Society of London, Volume 12.djvu/132 Page:Transactions of the Linnean Society of London, Volume 12.djvu/133 Cook's second voyage, and now in the library of Sir Joseph Banks, there is a figure of this plant, from which it appears that he originally referred it to Staehelina ”