1834 A TEXTBOOK OF THEORETICAL BOTANY 



source of Mahogany. African Mahogany is obtained from Khaya senega- 

 lensis. Cedrela odorata, also a West Indian tree, provides the Cedar wood of 

 commerce, while Melia azedarach is also an important timber tree. 



EUPHORBIALES 



The Euphorbiales are Archichlamydeae in which the flowers are usually 

 dioecious and hypogynous. They are generally actinomorphic, consisting 

 of a single whorl of free perianth leaves or occasionally the flowers may be 

 naked. The stamens are inserted opposite the perianth segments when 

 present, and are generally equal in number to them. Pollination is anemo- 

 philous. The ovary consists of three carpels, which unite to form three 

 loculi, the placentation is axile, each loculus containing one or two pendu- 

 lous, anatropous ovules, each possessing a ventral raphe. The growth of the 

 pollen tube is endotrophic. 



The classification varies considerably according to the views of various 

 authorities. According to Hutchinson, who is responsible for the name 

 Euphorbiales, it embraces the single family Euphorbiaceae. According to 

 Wettstein and Rendle the Euphorbiaceae are included in the Tricocceae 

 which also include, according to Wettstein, the Buxaceae, and according to 

 Rendle the Buxaceae and the Callitrichaceae. Engler on the other hand 

 includes the Euphorbiaceae in his Geraniales, in the sub-order Tricocceae, 

 and the Callitrichaceae in the sub-order Callitrichineae. He places the 

 Buxaceae in the Sapindales. Hutchinson separated the Euphorbiaceae 

 sharply from the other two families, referring the Buxaceae to the Hama- 

 melidales, a separate order made by him for certain of the Rosales (see 

 p. 1646), and puts the Callitrichaceae in the Lythrales, an order separated 

 from the older Myrtiflorae. 



Since we are only concerned here with the Euphorbiaceae, and since 

 that family is so distinct from the Geraniales, it seems best to follow 

 Hutchinson and use the order Euphorbiales as a monotypic one. The 

 Buxaceae and the Callitrichaceae have already been referred to. (See 

 p. 1809 and p. 1773.) 



Euphorbiaceae 



The family is essentially a cosmopolitan one though a number of small 

 herbaceous types occur in Britain. There are two British genera : Euphorbia 

 with some sixteen species, and Merciirialis, which is only represented by 

 two species. Among the more common members we may mention Euphorbia 

 helioscopia (Fig. 1736), the Sun Spurge; E. paralias, the Sea Spurge; E. 

 peplus, the Petty Spurge; E.peplis, the Purple Spurge; and E. amygdaloides, 

 the Wood Spurge. Mercurialis perennis is the Dog's or Herb Mercury. 



The plants vary very greatly in form and size and we should gain a 

 very wrong impression of the family merely from a study of the British 

 representatives. The latter are mostly small herbs, rarely growing above a 



