Characters of some little Icnozvn Genera of Plants. 177 



phous ; the imperfect forms of the one set of organs opposite 

 to the perfect ones of the other. The calyx we hav€ always 

 found to consist of two interior sepals, and three exterior, one 

 of which, and sometimes, but rarely all, are similar in size to 

 the interior, and alternating with them : there are in some species 

 in addition, small close-pressed bracteolae. The mode in which 

 the calyx is placed is well figured by De Candolle (Organ. Veg. 

 t. 37. f. 12. p.) We have, then, a calyx, a corolla, and andrce- 

 cium, each of five parts, placed apparently in a double series ; 

 the one dissimilar to the other, and alternate with it ; thus ana- 

 logically shewing, that the hypogynous disk must be viewed as an 

 outer series of the gymnoecium, the bidentate angles alternating 

 with the two cells of the ovary. At first also, it would appear 

 that the two outer parts of each organ alternate with the inner 

 of the next, but this is only in appearance ; for, if that were 

 the case, the angles of the hypogynous scale would be opposite 

 to the three larger petals, whereas they alternate with them. 

 The real disposition of parts, therefore, will be better under- 

 stood, if we suppose each organ to be of only one series, and of 

 five parts ; the petals alternating with the calyx, the stamens 

 opposite to the petals, and the pistilla alternating with both sta- 

 mens and petals. That this is the true explanation, is confirm- 

 ed by the fact, that, in no known plant, where any organ con- 

 sists of a double series of parts, do the component parts of one 

 series differ in number from those of the other. The aestiva- 

 tion will thus be imbricate and quincuncial ; and in such, two or 

 three (as may happen) parts of the same organ are interior. It 

 is, however, remarkable to find them of so very different a struc- 

 ture as occurs in tliis genus. 



The affinities of MiUingtonia have not, so far as we know, 

 been pointed out. The habit is much that of Semecarpus 

 mangifera, and Buchanania; and, like the Terehinthacece, the 

 embryo is campulitropal. The genus Sabia, also, has the sta- 

 mens opposite the petals, the ovarium bilocular, two ovules in 

 each cell, the one placed above the other ; but the petals are 

 likewise opposite to the sepals, and the habit is different : more- 

 over, it is by no means certain that Sahia ought to be referred 

 to the Terebinthacea ; and the characters of all the other ge- 



VOL. XV. NO. XXIX. JULY 1833. M 



