I ,v 



NATURAL HISTORY OF PLANTS. 



an Oceanian species very nearly connected with Acronychia, is distin- 

 guished from it by its simple leaves, pentamerous flowers, and 

 uniovulate ovary cells. 



Skimmia, consisting of Asiatic shrubs, with alternate simple 

 leaves, have polygamous-dioecious flowers with four or five im- 

 bricated petals, an isostemonous androceum, a 2-5-celled ovary, one 

 ovule in each cell, and a drupaceous fruit, the stones each containing 

 an albuminous seed, with one or several embryoes. Casimiroa 

 consisting of Mexican trees with an analogous floral formation, have 

 for fruit a large pomiform drupe, with monospermous stones but 

 exalbuminous seeds and the alternate leaves are compound-digitate. 

 Pliellodcndron, of which only one species is known, a native of 

 Manchouria, also has isostemonous flowers, but 5-8-merous poly- 

 dicecious pisiform glandular drupes, with five monospermous stones 

 and opposite imparipinnate leaves. 



Ptelea trlfoliata. 



Fig. 445. 

 Flower (f). 



Fia. 446. 

 Long. sect, of female flower. 



Pitavia nearly approaches the Zanthoxylons proper, and the Quas- 

 sias (Simarubece). In Pitavia, all the species being natives of America, 

 the flowers are unisexual, tetramerous, with imbricated corolla, eight 

 stamens, and independent ovaries, each supporting a gland above 

 and without. The fruits are drupaceous and indehiscent, and 

 the leaves opposite or ternate. In the Pentaceras of Australia 

 analogous to Pitavia by their independent ovaries, surmounted by 

 a gland, the pentamerous diplostemonous flowers are also consti- 

 tuted like those of numerous Simarubece : but the fruits are samaras, 

 and the alternate leaves imparipinnate. 



Ptelea (figs. 445, 446), often connected with Terebinthacea, con- 

 stitutes alone a subseries very remarkable by the organization 

 of the fruit. The flowers are polygamo-dicecious, 4-5-merous, 

 isostemonous, with a single ovary, and two or three biovulate 

 cells. The fruit is a widely-winged veined samara, with two or 



