and on the Structure of Hydnora africana. 233 



same natural class, in giving' an account of a new and remarkable genus of 

 the latter family*. 



At present I shall only remark, that the sole remaining character employed 

 to unite these two families and supposed to distinguish them from all others, 

 namely the simple or acotyledonous embryo, exists equally in Orchidece. 

 And if it be employed along with those characters connected with their 

 peculiar oeconomy, namely the imperfect development of leaves, the want of 

 stomata and absence of green colour, the class cannot be limited to Rafflesi- 

 acece and Balanophoreoe, for an embryo of exactly the same kind exists in 

 Orobanche, and other, perhaps all other, genera parasitic on roots, a remark 

 which I made, though not with sufficient precision, in my former essay. But 

 such a classification, though founded on seemingly very important technical 

 characters, would hardly be received in a strictly natural arrangement, and 

 it seems to me quite as paradoxical to approximate two such genera as Rqfflesia 

 and Balanophora. 



RAFFLESIA ARNOLDI. 



Rafflesia Arnoldi, R. B. in Linn. Soc. Transact, vol. xiii. p. 201. tabs. 15-22. 



Mas. 

 Rafflesia Titan, Jack in Malayan MiscelL, Append, to vol. i. 



approximated, their possible origin from one common basis or thallus is more readily suggested, espe- 

 cially on considering that in the former genus, which is dicEcious, each group of parasites is generally, 

 perhaps always, exclusively of one sex ; and that these groups, often of great density, not unfrequently 

 surround completely the branch of the stock. But although this view did occur to me as not very im- 

 probable, and as tending to remove some of the apparent difficulties, I have never been able to trace 

 any substance decidedly distinct from the proper tissue of the stock : there are, however, some appear- 

 ances favouring the hypothesis in both genera, especially in Pilostyles, but which require careful 

 examination in the living plants. 



* This genus, which was first found by Francis Masson, is the Mystropetalon of Mr. Harvey (in 

 South Afr. Gen. p. 418), who has described two species, from both of which Masson's plant is per- 

 haps distinct. 



I may here advert to a note at p. 225 of my former memoir (in Linn. Soc. Trans, vol. xiii.), in which 

 I thought it not improbable that a parasite briefly noticed by Isert (in Reise nach Guinea, p. 283) 

 might be related to Rafflesia. I have now, however, reason to beheve that Isert's plant is the Thon- 

 ningia sanguinea of Vahl (in Act. Soc. Hist. Nat. Hafn. t. vi. p. 124, t. 6, and Schumacher, Guineische 

 Plant, p. 431), a genus nearly related to, if really distinct from Balanophora. 



