DIV. n 



ANGIOSPERMAE 



653 



and arranged in a single whorl. The number of carpels is also increased. 



fruit is a berry ; the succulent 



portion is formed of large cells 



with abundant cell -sap which 



project into and fill up the loculi 



of the ovary. The seeds have 



usually several embryos (cf. p. 



578). The leaves of many species 



are simple and provided with more 



or less winged petioles. Other 



species have trifoliate leaves, and 



the articulation at the base of the 



lamina shows that the apparently 



simple leaves correspond to im- 



paripinnate leaves, 5f which only 



the terminal leaflet is developed. 



The thorns at the base of the leaf 



are derived by modification of the 



first leaves of the axillary bud. 



The 



FIG. 677. Floral diagram of Citrus 

 vulgaris. (After EICHLER.) 



Citrus is originally an East 

 Asiatic genus ; a number of 

 species inhabit the warmer 

 valleys of the Himalayas. 

 All the important cultivated 

 forms have been obtained 

 from the Chinese. Citrus 

 decumana, the Shaddock, is 

 tropical ; C. medico, is the 

 form which was known to the 

 Greeks in the expeditions 

 of Alexander as the Median 

 apple. It is now widely 

 spread and has a number of 

 varieties of which Citrus 

 (medico) Limonum is the 

 Lemon. This tree was intro- 

 duced into the Mediterranean 

 region in the third or fourth 

 century. Citrus (medico) 



FIG. 678. Citrus vulgaris. ( nat. size.) OFFICIAL. 



