514 NATURAL HISTORY OF PLANTS. 



inflorescence, that it has been rightly affirmed that there is scarcely 

 a collection in which they are not frequently confounded. True 

 Euphorbiacea may be often distinguished by the gynseceum formed 

 of two, three, or more carpels. But when these are solitary, as is 

 the case in Macarcmga, Eremocarpus, Antidesma, &c, with the flowers 

 moreover unisexual, and sometimes even achlamydeous, the only 

 remaining essential character lies in the more or less complete 

 anatropy of the. descending ovules. 



The geographical distribution of the thirty-nine genera (com- 

 prising some five hundred species) now admitted in this order pre- 

 sent some interesting features. According to Weddell, 1 " the New 

 World contains about a third ; Europe and Malaysia another third ; 

 Oceania and Africa divide equally nine-tenths of the remaining 

 third ; while Europe only claims a dozen species." Among these last 

 are five or six species of Nettles and Pellitories that multiply about 

 our dwellings. Some species of Urtica, such as U. dioica and urens, and 

 Parietaria, such as P. debilis, are spread over the temperate and sub- 

 tropical regions of the five quarters of the globe. U. urens extends 

 into the Arctic regions, nearly as much a cosmopolitan as P. debilis ; 

 indeed, it is that one of those species that accompany man everywhere 

 in his migrations. Near the Equator, where the Urticacea are the 

 worst weeds, we find a curiously unequal distribution between the 

 continents and islands. In the Tropical archipelagos the percentage 

 of species in the Phanerogamic flora is 5 to G ; in the neighbouring 

 continents it is only 2. 



The properties 2 of the Urticacece are unimportant ; were it not for 

 the stinging hairs, which make some species prized as urtkatinf 



1 Monogr., 41, 45. This work contains op- 6, ii. 328.— Kosenth., Syn. PI. Diaphor., 199, 

 posite page 552 a detailed table of the geo- 1108. 



graphical distribution, with the total number of 3 Therapeutical irritation is sometimes practised 



species representing each genus in the various in Europe with U. dioica L. or wrens L., more 



parts of each hemisphere. According to this rarely with U. pilulifera L. It causes a trail- 



summary, out of 476 species, the Old World sitory cutaneous irritation, sometimes very acute, 



contains 289, the New 187. due to inoculation with the acid liquid contained 



2 Endl., Enchirid., 170.— Ltnd., Yea. Kingd., in the stings (see p. 49S, note 3). 

 261 ; Fl. Med., 295.— Gtjib., B,og. Simpl., ed. 



