[ 81 ] 



III. Remarks on the Nature of the outer Jleshy covering of the Seed in the Clusiacese, 

 Magnoliacese, 8fc., and on the Development of the Raphe in general, wider its various 

 circumstances. By Joun Miers, Esq., F.R.S., F.L.S., Sfc. 



Read March 18th, 1856. 



IN a notice read before the Linnean Society on the structure of the seed of the Clusiacece, 

 I described the external fleshy envelope of the seed of the Clusiece, and offered evidence 

 to prove that this coating is a product of extraneous placentary growth, subsequent to the 

 development of the primine, and therefore a kind of ariUus. It was of some importance to 

 ascertain this point, as in the tribe Tovomitece of the same family, the outer coating, similar 

 in substance and coloui', is unquestionably an aril : this is manifest from its peculiar form ; 

 it is free from the testa, but may be opened out like a flat plate ; it is folded round the seed 

 which it envelopes and conceals, its margins being fi-ee and overlapping one another : in 

 the other tribe of the Garciniea;, this covering is also entire, is soft, and assumes the 

 character of an enveloping jiulp. If, therefore, in the two latter tribes, the outer coating 

 be unquestionably an aril, it was fair to conclude that the analogous envelope in the 

 Clusiaoete is of a similar nature. This inference was still farther confirmed by the 

 presence of a distinct simple raphe, which extends from the base to the apex of the seed 

 beneath the inner peUicle of the aril ; it lies within a groove of the testa from which it is 

 wholly free, the apex of which it perforates, and becomes lost in the chalaza of the inner 

 integimient. Under the evidence of such demonstrative proof, as far as regards the 

 Clusiece, I was led to institute a comparison of similar facts observable in the MagnoUacece, 

 because, if that coating be considered an aril in the one family, it must be of the same 

 nature in the other. I then referred to the admirable work of Dr. Asa Gray (' The 

 Genera of the Plants of the United States '), where a diffei'ent view is entertained : here 

 the external fleshy coat of the seeds of Magnolia is described as the testa, and its thick 

 bony shell as the tegmen, or inner integument, the true tegmen having escaped the 

 notice of that excellent botanist. In opposition to this view, I referred to the analysis I 

 had made many years before, of the seed of Talauma, a genus intimately allied to 

 Magnolia : the evidence then collected, convinced me that the ' testa ' described by 

 Dr. Gray is arUliform, and that his ' tegmen ' is the true testa. If we examine this outer 

 coating in Talauma, where it is entire, we find it easily detached from the testa or osseous 

 shell ; and if we begin to pull it away fi'om the summit, the raphe, as a distinct cord, wiU 

 be seen quite free from it, as in the Clusiece, and to lie in a corresponding groove which 

 extends from the base to the apex : the upper end of this raphe is seen to penetrate an 

 aperture near the summit of this osseous shell, and to become lost in the dark-coloixred 

 chalaza of a membranaceous inner integument. To all appearance, the raphe thus seems 

 quite free ; but if we examine it more attentively, a corresponding portion of the extremely 

 VOL. xxn. M 



