272 



NATURAL HISTORY OF PLANTS 



The Sumacs {Rhus) give their name to a subseries of Rhoidece. 

 They have polygamous flowers, with four or five parts (fig. 310, 311). 

 Their receptacle has the form of a surbased cone or of a tray on 

 whose edges are inserted an imbricate calyx and corolla. By this, 

 their flower recalls very much that of Schiims, as also by the gyna3- 

 ceum whose ovary is surmounted by three styles, free or united at 



Hhus Cotimis, 



Fig. 310. Female flower (f). Fig. 312._Fruit (f) Fig. 313. Longitudinal 



section of fruit. 



Fig. 311. Longitudinal 

 section of female flower. 



the base and stigmatiferous at the apex, but the androceum is nearly 

 always isostemonous, formed, in consequence, of four or five alterni- 

 petalous stamens, inserted below the edge of a thick disk. The 

 ascendent funicle supporting the only ovule may be inserted at 

 the base or more or less high on the side of the ovary, but it is not 

 attached above the middle of its height. The fruit (fig. 312, 313) is 

 drupaceous, the mesocarp often nearly dry, more rai-ely pulpy, com- 

 pressed, obovate, unsymmetrical or reniform ; its stone, hard, coria- 

 ceous or crustaceous, contains an inverted seed, with thin coats and 

 an embryo bent round upon itself ; the organic summit of the coty- 

 ledons and of the arched radicle are directed towards the summit of 

 the pericarp. This genus contains a hundred species from all the 

 warm and temperate regions of the globe. They are trees and 

 shrubs with resinous or burning poisonous juice, simple trifoliolate 

 or compound pinnate leaves, and very variable inflorescence. 



Beside the Sumacs are placed Comocladia, native of tropical 

 America, only distinguished by two characters of very slight value ; 

 the petals three or, more rarely, four in number with an equal 

 number of alternate stamens ; and a fruit which is drupaceous and 

 ellipsoidal, instead of being small and compressed or reniform, 



A small distinct group might be formed of the Pistachias 

 (fig. 260, 314-317) on account of the diminution of their 



