and on the Structure of Hydnora africana. 227 



the position of the included nucleus, but the very earliest stages I have not yet 

 distinctly seen ; while in Cyt'mus, in addition to the coat analogous to that of 

 Rafflesia and Hydnora, a two-lobed or bipartite membrane is observable. 



Of these three genera, I have hitherto observed the pollen or mucous tubes 

 only in Cytinus, in which they pass along the surfaces of a definite number of 

 cylindrical cords existing in the style until they reach the cavity of the ova- 

 rium, when they follow the direction of the placentae and become mixed with 

 the ovula, to which I have not yet, however, found them actually attached*. 



The structure of the pericarpium and the ripe seed of Rafflesia have been 

 satisfactorily ascertained from the examination of a single fruit found among 

 the numerous flower-buds in various states which were received from Sumatra 

 by Sir Stamford Raffles long after his return to England. In this fruit, which 

 is very accurately represented of the natural size in Mr. Bauer's figure, the 

 column, deprived entirely of its style-like processes, had become a compact 

 fleshy mass, having deep fissures on its surface dividing it into nearly square 

 lobes, somewhat resembling the surface of the dilated base of Testudinaria, 

 and within, like the ovarium, exhibiting irregular cavities, whose surfaces were 

 thickly covered with minute seeds. 



These seeds, which are also beautifully shown in Mr. Bauer's figures, difi'er 

 but little in form from the ovula of the expanded but unimpregnated flower ; 

 they are considerably larger, however, and the apex of the funiculus is still more 

 dilated. From their great hardness, as well as from their internal structure, 

 they appear to be quite ripe ; and it is worthy of remark, that of the many 

 thousands contained in the fruit, the very considerable portion seen were of 

 uniform size and appearance. 



The testa or outer integument, which is evidently that existing in the unim- 

 pregnated ovarium, is of such hardness and thickness that it may be termed a 

 nut ; it is of a chestnut colour, its surface regularly reticulate and deeply pitted, 

 a depression occupying the centre of each areola. 



The inner integument is a thin light-coloured membrane, very slightly 



* In a few cases where the supposed pollen tubes were present 1 found them applied to the apices 

 of the enlarged ovula. In some instances I have met with only a very loose tissue, consisting of 

 elongated cells mixed with mucus, forming cords descending from the stigmata, and reaching to, but 

 not extending beyond, the origin of the placentae. 



VOL. XIX. 2 H 



