IN THE CLUSIACE^, MA.GNOLIACE.E, ETC. 89 



EncUiclier calls it a fleshy raphe, but this oi-igin is evidently due to the same soirrce as 

 that of the outer tunic of 3Iag)ioUa. 



It is here necessary to point out the distinction between the different kinds of arilli- 

 form coatings of the seed. We have strong evidence to show that the scarlet covering in 

 the ClusiecB, Magnoliacea;, &c., is derived from a growth of the placentary sheath, which 

 is a production of the funicular cord, whose origin is coajval with the anatropal inversion 

 of the ovule : other cases however occur, where another still more exterior development 

 is generated at a subsequent period : this is well known to proceed from the main 

 placenta, or more often from the short funicular cord, which is the foot-stalk of the 

 placentary sheath by which the ovule is attached, sometimes forming a thick ciip as in 

 the Sapindacece, &c., or at other times extending itself like a fleshy, coloured plane sheet 

 completely enveloping the seed, as in the Tovomitece, or which form branching fleshy 

 segments embracing the seed, as in Myristica, Samydacece, &c. These several varieties 

 derive theii- origin from a growth of the placenta and are not developed from the 

 original coats of the ovule ; they are therefore arilliform in their nature, but as they are 

 produced under different circumstances, I propose to confine the term aril (arUlus) to the 

 kinds of coating last described, always void of spiral vessels, and to denominate that sort 

 found in the Clusiece, MacfnoUacece, &c., the arilline (arilb'nus), in which the vessels of 

 the raphe are always imbedded. Both may and often do exist at the same time, in the 

 same seed, or they may make theii' appearance independently of each other. 



There is said to be still another kind of extraneous fleshy coating, produced over the 

 testa in the maimer fii-st pointed out by St. HUaire, to which he gave the name of false 

 aril, and which was afterwards ably investigated by Dr. Planchon, who substituted for it 

 the name of arUlode*. This tunic is described as originating in the expansion or rever- 

 sion {dedoublement) of the mouth of the exostome or foramen of the primine, which 

 gradually extends itself over its Avhole surface, and forms an extraneous envelope around 

 the testa. The formation of the arillode from such a source, rests upon the authority of 

 Dr. Planchon, to which I attach its due weight ; and although in support of his views, he 

 described, with great minuteness!, the gradual formation of the arillode in Euonymiis 

 latifolius, it is certain that in drawing the conclusion that the arillode proceeds from the 

 extension of the exostome, he expressed at the same time some misgiving on the subject |. 

 Examining therefore the details as there represented, and comparing these with my own 

 observations on the seed of Euonymus, I think it may be inferred, with equal, if not with 



* Mem. ante cit. p. 10. f Idem, p. 7. 



X " En disant que ce dernier sac (le faux arille) procfede uniquement de I'exostome, peut-etre ai-je un peu sacrifi# 

 I'exactjtude a la clarte. Comma I'ombilie, en effet, est tres voisin du mieropyle, 1' expansion arilliformc partant des 

 bords de ce dernier, devrait rencontrer dans le funicule un obstacle a son extension et offrir une solution de continuity. 

 Mais c'est IJl au contraire que F expansion est la phts ipaisse, et meme elle adhire avec la base du raphe sur une partie 

 de sa longueur de maniire it ce qu'elle semble sur ce point nmtre de cette dernibre partie. II faut done necessairement, 

 pour expliquer une pareille disposition, admettre une soudure congeniale entre l' expansion et le funicule. Je crois 

 devoir ajouter pour prevenir tons les doutes, que chez les Euonymus, le mieropyle est fort difficile tl voir, lorsque 

 I' ovule est dija tris dcveloppi, parceque le faux arille est plissi autour de son ourerture, et la cache compUtement : 

 niais en di'tachant avec soin I'enveloppe accessoire, on peut facilement s'assurer qu'elle nait des bords de rexostome." 

 — //oc rit. p. 9. 



VOL. XXII. N 



