168 RHAMNACE^. 



raphe of tlie ovule becomes lateral, or even external, in several genera of 

 this family, namely, by the twisting of the short funiculus. This displace- 

 ment is best observed in Rhamnus, in which it is easy to see 'that the raphe 

 of the ovule is internal, while in the seed the groove in which it is received 

 is exterior. 



This family, comprising about forty genera and two or three hundred 

 known species, is represented in almost every flora except the arctic and 

 antarctic ; but is most abundant in the warmer part of the temperate zones 

 and along the borders of the tropics. In the southern hemisphere the great- 

 er number are South African and Australian, and are of peculiar forms. 

 The North American genera all belong to the tribe FrangulecE. 



A bitter extractive principle abounds in the bark, with more or less as- 

 tringency and acridity. Some are purgative or emetic, w'hile others, as the 

 Quina of Brazil (Discaria febrifuga), yield an extract which is valued as a 

 tonic and febrifuge. The bark and root sometimes yield a coloring matter, 

 as also do the rather mucilaginous, nauseous, and often cathartic fruits of 

 several species of Rhamnus. But the fruit of Zizyphus, especially of the 

 Lotebush and Jujube, is esculent. The dried leaves of Sageretia iheezans 

 are used by the poorer classes in China as a substitute for tea : those of Ce 

 anothus Americanus have been similarly employed in this country. 



Conspectus of the United States Genera. 



* Drupe baccate or fleshy; the putamen bony, one -three-celled. Ovary 



immersed in the thickened disk. 

 Zizyphus. (Plate 163.) Calyx-tube expanded, connate with the base of 



the ovary. Petals 5. Drupe baccate ; the putamen 1 - 3-celled. 



Albumen almost wanting. Cotyledons very thick and fleshy. 

 CoNDALiA. (Plate 164.) Calyx free. Petals none. Putamen one-celled. 

 Berchemia. (Plate 165.) Calyx free. Petals 5, entire. Putamen 



crustaceous, 2-celled. 



* * Drupe baccate ; the putamen separating into 2-4 nutlets. Calyx free. 

 Sageretia. (Plate 166.) Disk thick and fleshy, surrounding the ovary. 



Drupe 3-pyrenous. Cotyledons plane. Leaves opposite. 



Frangula. (Plate 167.) Disk thin, lining the calyx-tube. Drupe 2-4- 

 pyrenous. Seeds not sulcate ; raphe lateral. Cotyledons plane, fleshy. 



Rhamnus. (Plate 168.) Disk thickened at the margin, lining the calyx- 

 tube. Drupe 2-4-pyrenous. Seeds sulcate on the back, the raphe 

 in the groove (dorsal). Cotyledons foliaceous, their margins revolute. 

 * * * Fruit at first drupaceous, soon dry and tricoccous. 



Ceanothus. (Plate 169.) Calyx colored ; the lobes inflexed, shorter than 

 the unguiculate petals and filiform filaments. Seeds not sulcate. 

 Cotyledons plane. 



