PHAXEROGAMIA 



617 



inverted female flower hangs down in the gap left. Between the groups of male 

 flowers, which stand opposite to the bracts (Fig. 660), are branched hairs which are 

 visible when the cyathium is cut through longitudinally (Fig. 662 B). The cyathia 

 are usually grouped in dichasia, and these in turn form an umbellate inflorescence, 

 with three to many branches. It often happens that the female flower is only 

 developed in some of the cyathia, remaining rudimentary in the others. Many 

 species of Euphorbia, especially the African species, are succulent-stemmed plants 

 resembling Cacti in general appearance (cf. Fig. 661). 



Euphorbia, like many but not all the other plants of the family, contains a 

 milky juice, which is secreted in non-septate latex-tubes. This juice, which in 

 many cases is poisonous, exudes wherever the plant is wounded. 



KK:. i id-.'. l-:nj, !,,,,!, : t i T.iitlnirit. A, Cyathium (x .~0. /;. C.vathium cut thruuf;h longitudinally 

 (x 7). C, Fruit alter dehiscence showing the centv;il column (<). /', Seed in longitudinal 

 section showing the embryo embedded in the eiid<|>enn ; <", caruncuKi (x 4). (A-D after 

 BAILLON.) 



An important constituent of the latex of species of Hevea (If. Uiebcri, discolor, 

 rigidifolia, pattoifolia, lutea, guyancnsis, Spruceana) is CAOUTCHOUC. As Para 

 Rubber obtained in the tropics of South America, especially in the Amazon region, 

 this affords about one half of the total rubber supply. In addition Manihot 

 Glaziovii, another South American plant of this order, which yields Ceara Rubber, 

 must be mentioned. A nearly related plant, Manihot utilissima, provides in its 

 tuberous roots a very important food in the tropics. The starch obtained from 

 these roots forms mandioc or cassava meal, the finest varieties of which, as tapioca 

 or Brazilian arrowroot, are of commercial importance. The shrub, which is a 

 native of Brazil, is now cultivated throughout the tropics. 



Ricinus communis (Fig. 663) is a tall shrub of tropical Africa. In our climate 

 it is annually killed by the frost. The hollow stem bears large palmately divided 

 leaves. The terminal inflorescences (Fig. 664) are overtopped by vegetative lateral 



