SECT. [I 



PHANEROGAMIA 



563 



tlie other liaml in the seed ; tlie separation of the later from the placenta is assisted 

 by it. 



The fruit is a capsule, the outer walls of which contract elastically 

 away from a central column, and thus open the loculi. 



The plants of this family are distributed over the whole earth. Important 

 Gener.\. — Many Euphorbiaceae are dioecious or monoecious, and have flowers of 

 relatively simple construction. Thus Mecuriahs (Fig. 538), two species of which 

 occur in Britain, is characterised by its bicarpellary ovary. Croton is a tropical 

 genus including valuable official plants, C. Eleuteria and C. Tvjlium ; the male 

 Howers have a double, the female Howers a single perianth. In the Spurges 



Fig. 5i2.—EuphorUa Lathyris. A, Cyatliium (x 5). B, Cyatbium cut through longitudinally 

 (X 7). C, Fruit after dehiscence showing the central column (c). D, Seed in longitudinal 

 section showing the embryo embedded in the endosperm; ca, caruncula (x 4). (A-D after 

 Baillon.) 



[Euphorhia), of which there are several British species, a number of the extremely 

 simply constructed flowers are grouped in a complicated inflorescence termed a 

 CYATHIUM (Figs. 539-542). This consists of a naked, terminal, female flower, 

 borne on a long bent stalk surrounded by a number of groups of male flowers. 

 Each of the latter is stalked and consists of a single stamen, the limit between 

 which and the flower-stalk is distinguishable. In some cases the female flower 

 and each male flower are provided with a small perianth. The whole cyathium, 

 which is an inflorescence, is always enclosed by Ave involucral bracts ; alternating 

 with these are four nectar-secreting glands, the presence of which increases the 

 likeness between the cj'athium and a flower. The fifth gland is wanting, and the 

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

 flowers which stand opposite to the bracts (Fig. 540), are branched hairs which are 

 visible when the cyathium is cut through longitudinally (Fig. 542 B). The cyathia 



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