-.fts-^o^vv Ml*. J. Miers on some genera of the Icacliiaccae. 481 



.^jXL» — On some genei^a of the Icacinacese. By John Miers, 

 tfif Esq., F.R.S., F.L.S. 



[Continued from p. 399.] 



PORAQUEIBA. 



No botanist has ventured to assign a position in the system to 

 this very curious genus of Aublet until very lately, when M. 

 Tulasne has given a description of it in the 11th vol. (3rd ser.) 

 of the 'Ann. Sc. Nat.,^ where he has very correctly referred it to 

 Mr. Bentham^s tribe of the Icacinece. The analysis given in 

 plate 47 of Aublet^s work, though roughly drawn, is in the main 

 correct, and the details there shown will be more easily com- 

 prehended from the particulars I am now able to offer. The 

 singular partitions that stand in bold relief on the inner surface 

 of the petals, are produced by their pressure, while in bud, upon 

 the enclosed genitals ; the force of this compression is such, that 

 a portion of their fleshy substance is forced between the in- 

 terstices of the curiously formed stamens, stamping a counter 

 mould of their shape in the raised lines and deep cells that con- 

 stitute the peculiar character of the petals j the upper and trans- 

 verse portions of the very elevated cruciform partitions thus pro- 

 duced are deep, while the lower pale is broad and hollow in its 

 centre, forming in this manner two very deep cells in the upper, 

 and three parallel cells in the lower moiety. This however, as 

 might naturally be expected, proves to be a variable character, 

 for in a new species described by M. Tulasne, the two upper 

 cells and the intervening deep keel are deficient, owing, it would 

 appear, to the circumstance of the anthers being only half the 

 length of those of the other species, so that the lower moiety 

 only of each petal presents two cavities in which the stamens are 

 lodged in the bud. The stamens are of very singular construc- 

 tion, and the figure in Aublet^s drawing affords a very ex- 

 aggerated idea of their form. In all the preceding genera, I 

 have described the bilobed anthers as being always distinctly 

 4-celled before they burst, although after dehiscence, from the 

 evolute mode of opening, they appear as if they had been only 

 bilocular. In Poraqueiba, however, this 4-celled structure is 

 rendered manifest in a much higher degree, for the cells are here 

 perfectly distinct, and even separated from one another for a 

 considerable distance by the intervention of a thick 4-sided 

 pyramidal connective, composed of coarse reddish-coloured 

 grains : this is covered by a whitish adhering cuticle, consisting 

 of a thicker crustaceous epidermis, and a thinner and more 

 membranaceous inner tegument ; the narrow cylindrical pollen- 



