616 



BOTANY 



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

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



IMPORTANT GENERA. Many Euphorbiaceae are ditecious or IIIOIKH inii.s, and have 

 flowers of relatively simple construction. Thus Mercurialis (Fig. 658), 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. Tiglium. In 

 the Spurges (Euphorbia), of which there 

 are several British species, a number of 



!'!<;. MO. Diagram Of a ilichasial liranrh nf 



Ma, with three cyathia, only the inicldl i. <.t 



which has a fertile female flower. (After EICRI.F.I:.) 



Fui. 651'. Euphorbia ciiparifniii* O nat. si/e). l-'n.. iir.1. />;./.. i///m ntM/era. (Nat. si/e. 



PoffiOXot'x. After BEIU: and SCHMIDT.) 



the extremely simply constructed flowers are grouped in a complicated inflorescence 

 termed a CYATHIUM (Figs. 659-662). This consists of a naked, terminal, female 

 flower, borne on a lung 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 bct\\e.-n 

 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 five involucral bracts ; alternating 

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

 likeness between the cyathium and a flower. The fifth gland is wanting, and the 



