26 Mr. J. Miers on the Development 



ovary is a feature very distinct from that of its relation to the 

 raphe ; and the two should not be confounded together : thus in 

 Rhamnus catharticus the raphe is dorsal, both with respect to 

 the axis of the ovary and to the embryo ; in R, chlorophorus it 

 is dorsal with regard to the embryo, but lateral as respects the 

 axis of the ovary. In most instances throughout the Rhamnacece 

 the embryo is incumbent with respect to the ovary, one of its 

 cotyledons being posterior, the other anterior, in regard to the 

 axis ; but it is accumbent in regard to the raphe, which skirts 

 the margins of the cotyledons. In Berchemia the cotyledons 

 are incumbent, both with regard to the ovary and to the dorsal 

 raphe. 



In this investigation, I have noticed only the proper integu- 

 ments of the ovule, leaving out of consideration that coating 

 which, after impregnation, frequently grows over the primine 

 and produces in the seed either an incomplete or an entire tunic, 

 called an arillus, Schleiden and others are of opinion that the 

 true aril must necessarily be pervious at its extremity, and he 

 concludes (/. c. p. 431) that wherever an actually closed structure 

 surrounds the seed, it is undoubtedly a layer of the seed-coats : 

 but this is mere opinion unsupported by proof ; for it is equally 

 probable that the aril may become closed just as much as the 

 proper tunics of the ovule. It has also been thought that it must 

 necessarily be fleshy ; but I have shown* that it is often perfectly 

 entire, and frequently hard and testaceous (as in Canellacece, 

 Winter acece, &c.), in which case the true testa, or development 

 of the primine, is generally either fleshy or membranaceous, 

 contrary to its usually hardened condition. 



Where, on the other hand (as in Magnolia^ Clusia, &c.), the 

 inner tunic of the ovule becomes hardened by osseous deposits, 

 the primine, as in the former case, remains fleshy, and assumes 

 the appearance of a complete arillus, for which reason I proposed 

 to call it an arilline^ instead of testa, to which name the hard- 

 ened tunic is more entitled. It has been contended by Dr. Asa 

 Gray that the osseous tunic and the aril-like covering which 

 contains the cord of the raphe are both developed from the pri- 

 mine, the former resulting from hardened deposits upon its 

 inner layers of cells, while the outer cells remain soft and 

 fleshy. I have argued that, if such a deposition took place 

 in the manner stated, these two dissimilar textures must be en- 

 closed by a single epiderm and one endoderm ; but we find, on 

 the contrary, each of the tunics provided with its respective ex- 

 ternal and internal epidermis, showing that the two formations 

 are independent in their origin. It is also clear, that if these 



* Ann. Nat. Hist. 3 ser, ii. 39; Contributions to Botany, i. 128. 

 t Trans. Linn. Sec. xxii. p. 89. 



