L YTHRAR1ACEM. 445 



of generic groups ' to twenty-two. The number of species is esti- 

 mated at about two hundred and fifty. 



The geographical distribution is very extended. Cuphea, entirely 

 American, comprises more than a third of the species of the family. 

 Lythrum and Ammanma, each giving a name to a series, are spread 

 over a very vast area, in the new as well as in the old world, in 

 tropical as well as in temperate regions. Peplis portula, in the north 

 of Europe, corresponds to Ammannia, found in North America, 

 Australia, and the Cape of Good Hope. Salicaria from Lapland and 

 the north of Asia to Tasmania, the Cape, and southern Chili. Ten 

 genera are exclusively American, and three are common to America 

 and the old continent. Pemphis, represented by a single species, 

 conforms to the litoral plants which resemble it ; it is met with in a 

 great part of tropical Oceania and Asia. Lmvsonia, supposed to be 

 a native of the north-east of Africa and of India, has been introduced 

 into many tropical countries. Most of the old world genera are 

 limited to a few countries. Tetrataxis belongs exclusively to Mau- 

 ritius, Psiloxylon to the Mascarene isles, Grypteronia to Malaya and 

 the Philippines. Bhyacophila and Woodfordia are common to central 

 Asia and eastern Africa. 



The characters absolutely constant in this family are very few. 

 The concavity of the receptacle of little thickness but very deep, the 

 perigynous insertion of the corolla, when it exists, and especially the 

 independence of the gynascium situated at the bottom of the recep- 

 tacular cavity, are about all that can be mentioned. By the last the 

 Lythrariaceœ are distinguished from the Myrtaceœ and Onagrariaceœ, 

 to which they are allied by all other characters, and which, in all 

 normal 'types, have, as is said, "the ovary adherent." The Bhizo- 

 phoracece with free ovary, that is the Macarisiece, are in this respect 

 nearer the Lythrariaceœ with which several of them have been 

 confounded ; 2 but in the latter, the ovules in each cell are indefinite 



'Without counting the genua Physopodium -with precision. P. volubile, a climbing shrub of 



ofDESYAvx [Aim. Sc. Nat. ser. 1, ix. 403) gene- Bourbon, is perhaps a Combretacece ; we have 



rally enumerated in the Lythrariaceœ (DC. been unable to discover it in the herbarium of 



Prodr. iii. 94 ;— Endl. Gen. n. 6168), the place Desyai x. 



of which is not determinable, the characters of - Especially Symmetria Bl. which is a Sarral- 



the gymecium and of the fruit not being given diia and Tomostylis Montkous. [Mem. Acad. 



