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gation for large barges, it is presumed, will, notwithstanding, be impeded for an hour or two each tide, at and during the time of low-water, particularly at spring-tides.
It was not, however, my intention, in this paper, to do more than record the preceding particulars, for the purpose of comparison hereafter. I shall not, therefore, enter farther upon the probable changes which the removal of the bridge may occasion; a short time will decide the question, by the best of all tests, actual experience.
On the Affinities of the Empetreæ, a natural Group of Plants.
By Mr David Don, Libr. L. S. &c. Communicated by the Author.
I am aware that it has already been proposed to separate Empetrum from the Ericeæ*; but the mere removal of it from that family, was nothing more than what Jussieu himself had previously done. That its relative affinities have hitherto been entirely overlooked, no one who has given the least attention to the investigation will for a moment question; and it would only be a waste of time to attempt to point out the discrepances between the Empetrea and Ericea, or between them and Conifera, of which Nuttall is disposed to consider them as a section t; for, with the exception of a slight resemblance in habit, there is really neither analogy nor affinity between them; nor do the Empetree even belong to the same natural class with either of these families. I have, however, lately discovered a remarkable affinity between this group and Euphorbiacea, as well as Celastrine, which it is my principal object in this paper to point out; but, as they appear to me to be more intimately allied to the former, the comparison will be chiefly confined to these two tribes. The Euphorbiaceæ and Empetreæ agree, therefore, in the imbricate æstivation of their calyx; in the stamens being opposite to the divisions of the calyx, and both these being of an
* Nutt. Gen. 2. p. 233.
+ Nutt. I. c.
equal and definite number; in having bilocular anthers; in their superior ovarium; in the plurality of styles; in their divided stigmas; and, lastly, in the arrangement of the ovula, and presence of a copious albumen. The embryo is also nearly the length of the albumen, and its cylindrical form brings it close to that of Phyllanthus. The male inflorescence of Empetrum album has a striking analogy to that of Buxus *, whose calyx consists of 3 or 4 leafets, with the stamens equal in number, and placed opposite to, not alternating with them ;-a circumstance which proves that this organ in Buxus is a true calyx, and not, as Linnæus regarded it, a corolla. In separating the Empetrea from Euphorbiacea, the principal character relied on is their erect embryo; for in habit they are not far removed from Micranthea of Desfontaines, some species of Phyllanthus, or even of Euphorbia itself. In Phyllanthus, the calyx consists of 6 segments: the filaments are 3, closely united together; and the anthers are 4 in number, 3 of which are lateral and alternate with the inner divisions of the calyx, which are probably to be regarded as petals. The fourth anther, which may be considered as spurious, is placed directly in the centre of the 3 lateral ones. In a decandrous species of this genus from Mexico, each of the filaments is trichotomous, and each branch bears an anther of the usual structure, which, together with the central one, augments the number to 10. In the female flower, the styles are 3, united at the base, and the stigmas are divided into two lobes. The fruit is 3-sided and 3-celled, each cell containing two seeds placed parallel, and opening at the angle by a longitudinal suture; these sutures are immediately perpendicular to the styles, and placed opposite the exterior segments of the calyx. I ought to have before remarked, that the form and structure of the anthers of Euphorbia and Empetreæ are exactly similar. The monophyllous calyx; the non-separation of the sexes; the presence of a perigynous disk ; and the flat, somewhat foliaceous cotyledons,-appear to separate sufficiently the Celastrinæ from the Empetrea. The distinctions between them and the Rhamnee are still more apparent, however ; for in them, the stamens are placed opposite the petals, and the æstivation of the calyx is valvular,—characters of primary importance in a natural classification. The embryo in Rhamneæ and Celastrinæ agrees exactly in form and structure. Mr Brown has very properly placed Phylica among the Rhamneæ, although I have known some who, merely from the fruit being inferior, were disposed to remove it from that family. It is evidently intimately allied to Pomaderris, both in habit and characters, and it is equally evident, that the fruit being inferior, is a distinction more apparent than real; for in Pomaderris, and even in some species of Rhamnus, the tube of the calyx coheres with the ovarium ; and could we, for example, suppose an equal elongation of the tube of the calyx in these, as in Phylica, we should then have the situation of the fruit precisely the same. The apparently simple stigma in Phylica is not very different from the triple one of Pomaderris; for there is evidently an indication of three distinct lobes.
* In the Prodromus Flore Nepalensis, I have very briefly noticed a plant under the name of Buxus Saligna, and which I then suspected would even. tually prove a distinct genus; but materials are still wanting to determine this point satisfactorily. From the very imperfect description given by me, Mr Lindley, in a late number of the Botanical Register, has been induced to suspect its being only a variety of his Sarcoccoca pruniformis ; but the fol. lowing description will shew that it has very little affinity to that plant.
Buxus Saligna, Don, Prodr. Fl. Nep. p. 63. Flores dioici ? Fem.Calyx squamis pluribus (6-8). Ovarium ellipticum,
3-loculare: ovulis solitariis. Stigmata 3 (raro 4) lanceolato-subulata, acuta, revoluta, suprà convexa, tomentosa, sulco exarata, subtùs nuda. Fructus (immaturum tantùm vidi) 3-locularis (raro 4-locularis), stigmatibus persistentibus rostratis, et inter rostra foramine dehiscens : loculis monos permis. Dissepimenta membranacea. Frutex erectus, ramosissimus, frondosus, sem. pervirens. Folia alterna, nunc rarò subopposita, petiolata, angustè lanceolata, acuminata, integerrima, basi acuta, margine reflectente, pagina utraque diversâ (ut in Buxo), coriacea, enervia, glaberrima, nitida, subtùs venis parum conspicuis, 3-pollicaria, semiunciam lata. Pedunculi axillares, breves, divisi, pluriflori, subracemosi, cernui.
ERICEIS AFFINIA, Juss. FLORES dioici. Masc.-Calyx 3- (rarò 2-) phyllus, æstivatione imbricatâ, basi nu
dus v. squamis (4-6) duplici ordine imbricatis munitus. Petala 3 (rarò 2) hypogyna, foliolis calycinis alterna, ungui brevi, limbo obovato concavo erosè crenulato, marcescentia. Stamina totidem, iisdemque alterna, hypogyna, exserta, paululum interiùs seposita, pariter marcescentia: filamenta longiuscula, angustissima, compressa, glabra: antheræ subrotundæ, biloculares, subdidymæ, ad medium peltæ modo filamentis impositæ: loculis ventricosis, ferè omnino solutis, rimâ longitudinali exteriùs
dehiscentes. Ovarii rudimentum. Fem.--Calyx maris. Petala totidem, sed breviora et vix ungui
culata. Staminum rudimentis rarò ullis. Pistillum : ovarium globosum, sessile, disco carnoso impositum, 3, 6, v. 9-loculare, ovulis solitariis: styli 3, brevissimi, in unum corpus triangulare coaliti: stigmata radiato-multifida : lobis 6 v. 9, patulis, basi dilatatis, subtùs percurrenti-carinatis, suprà sulco perangusto exaratis, pruinosis, apice truncatis, emarginatis v. bicorniculatis. Bacca sphærica, nunc depressa, apice leviter umbilicata, basi calyce persistente cincta, 2, 3, 6 v. 9-pyrena: caro parca: pyrenæ testâ osseâ monospermæ, erectæ, collaterales, elliptico-trigonæ, compressiusculæ, columellæ demum evanescentis angulis numero æqualibus per totam longitudinem adnatæ, dorso convexo sulcato, ad apicem puncto exiguo ferè perviæ. Semen ovoideum, cavitati pyrenæ conformis, basi chalazâ tuberculiformi atro-fuscâ instructum : testa simplici, membranaceâ, spadiceâ, reticulato-vasculari, apice puncto notatâ : albumen copiosissimum, densum, carnosum, aqueo-pallidum, hinc facie planiusculâ, inde convexum. Embryo teres, erectus, axilis, lacteus, albuminis ferè longitudine: cotyledones semicylindricæ, obtusæ, arctè applicatæ: radicula infera, recta, cylindracea, obtusa, co
tyledonibus ferè triplo longior. Frutices (utriusque orbis zonis temperatis proprii) humillimi, sem
pervirentes, facie ericoidea. Folia alterna, petiolo exigui complanato suffulta, margine revoluta, integerrima, exstipulata. Flores parvi, axillares solitarii, v. terminales glomerati.
Calyx 3-phyllus, coriaceus, basi squamis 6 imbricatis munitus.
Petala 3. Stamina 3. Stigma 6-9-fidum. Bacca depressa,
6-9-pyrena. Fruticuli (Europ. bor. et Magellan.) ramosissimi, procumbentes.
Folia alterna, lincari-lingulata, obtusa, suprà plana, subtùs convexa et lineâ membranaceâ exarata, atro-viridia, nitida. Flores axil
lares, solitarii, sessiles, atro-sanguinei. Baccæ nigræ v. rubræ. Hùc E. nigrum, L. et E. rubrum, Vahl.
EMPETRI sp. Linn. Juss. Calyx 3-phyllus, membranaceus, basi nudus. Petala 3. Stamina 3.
Štigma 6-fidum. Bacca globosa, 3-pyrena Suffrutex (Europ. austr.) erectus, ramosissimus, rigidus, punctis re
sinosis adspersus. Folia undique sparsa, linearia, obtusa, patula, suprà planiuscula, margine revoluta. Flores terminales, glomerati, sessiles, disco piloso impositi, albi, majores. Capitula squamis vil
losis bracteolata. Baccæ albæ. Hùc E. album, L,
CERATIOLA, Rich. in Mich. Fl. Amer. bor. Calyx 2-phyllus, membranaceus, basi squamis 4 munitus. Petala 2,
in tubum conniventia. Stamina 2. Stigma 6-fidum. Bacca
globosa, 2-pyrena. Suffrutex (Amer. bor.) adscendens, ramosissimus, rigidus. Rami stricti
, simplices. Folia alterna, patentia, acerosa, obtusa, glabra, nitida, viridia, subtùs sulco angustissimo exarata, suprà leviter canaliculata, semipollicem longa ; nunc plurima approximata, quasi verticillata. Flores axillares, sessiles, plures (2-4), rarò solitarii ; nunc (ad folia approximata scilicet) verticilli modo dispositi. Bac
c rubre 2 Hùc Ceratiola ericoides, Rich. in l. c. 2.
In order to render this treatise as complete as possible, besides giving a description of the group itself, I thought it important to add the characters of the genera. It is immaterial whether the Empetreæ are to be regarded as a section of the Euphorbiacee, or as constituting a separate family. Their intimate affinity has, I trust, been satisfactorily shewn; and it also appears clearly evident, that the Euphorbiaceæ, Stackhouseæ, Celastrinæ, and Rhamneæ, must follow each other in a natural arrangement, as Mr Brown seems disposed to think *.
• General Remarks on the Botany of Terra Australis.