as distinguished from the Symplocaceoc. 129 



so essentially clifFerent in these two groups j and althougli these 

 last-mentioned features are respectively given in the generic 

 details of Si/mplocos and Stijrax, no inference in an ordinal point 

 of view has been drawn from structures so totally distinct, and 

 which it is difficult to reconcile under the same category. 



Before I proceed to consider the affinities of these two groups, 

 I will offer some details of the structure of their ovary, as well 

 as of their fruit and seed. In the SymplocacecB we have an 

 ovarium composed of five (rarely fewer) carpels completely 

 united around a central axis, which is placentiferous in its upper 

 portion and continuous with the style, so that the cells are per- 

 fect and sei)aratcd by as many complete partitions, which retain 

 their integrity in the ripe fruit. In those cases where some of 

 the cells are occasionally abortive, even where only one cell is 

 perfected, the reiiiains of the other cells, together with their 

 previous axis, may always be distinguished in that portion of 

 the paries which is thickened about that line. Hence it con- 

 stitutes an essential feature in this family to have a plurilocular 

 ovary, the margins of its carpellary leaves being always placen- 

 tiferous and united together in the axis, so that the cells thus 

 formed are complete from the base to the apex. 



On the other hand, in StyracecB we find a central placentation, 

 more or less abbreviated, sometimes almost obsolete, which has 

 never any connexion with the style, and hence the summit of the 

 ovary, in a greater or less degree, is always unilocular ; the pla- 

 centa thus generally rises very little above the base of the central 

 space, although it is sometimes elevated above the middle of the 

 cavity : in all these cases the bottom of this central space is 

 divided by three (in Halesia by four, and in Fterostyrax by five) 

 short partitions, which unite with the central placenta, and, 

 under the form of prominent parietal uervures, are continued up 

 the wall of the ovary to near its summit, which always remains 

 unilocular ; but neither these nervures nor the margins of the 

 short partitions of the basilar incomplete cells exhibit any ovules. 

 The abbreviated central placenta is thick, fleshy, and ovuligerous, 

 bearing frequently more than thirty ovules, that is to sa}'', ten or 

 twelve in each division, arranged in three or four rows, its sur- 

 face being corrugated by as many fleshy projections imbricated 

 on one another, and between which the ovules are imbedded to 

 some depth : this process is not, however, observable in Halesia. 

 Nothing approaching this structure exists in Symjilocacece. From 

 these facts we may conclude that the normal condition of the 

 component carpels in Styracece is that their margins are never 

 placentiferous, and do not unite in a solid axis, and consequently 

 are never continuous or connected with the style ; and the in- 

 ference, in a theoretical point of view, is that the origin of the 



Ann, ^ May, N, Hist, Scr. 3. Vol. iii. 9 



