14 NATURAL HISTORY OF PLANTS. 



smaller number in Asia and Madagascar. The genera Abronia, 

 Okenia, Nyctaginia t Pentacrophys, Selinocarpus reduced to one, or a 

 small number of species, only inhabit the south-western regions of 

 North America. Boldoa and Colignonia extend farther south, in the 

 west of South America. Allionia occupies a long western zone from 

 Mexico to Chili. Oocybapltus is wholly American, except one Indian 

 species, which occupies the sides of the Himalayas. Mirabilis is 

 solely American ; but M. Jalapa has been introduced into all the 

 warm and temperate countries of the globe. 1 



The Nyctaginacea have been considered as allied at the same time 

 to the Polygonacea, Chenqpodiacea, Pfambaginacece, Phytolaccacea, 

 Cannabinacece, Valerianacece, Piperacece. Despite of external 

 resemblances, they are sharply distinguished from the first three 

 families, for in these the basilar placenta bears the ovule, around 

 which the wall of the ovary is formed by the union of two or several 

 carpellary leaves. The Cannabinacece have also more than one 

 carpellary leaf to the gynseceum and an axile placenta supporting a 

 single descending ovule in the fertile cell. The Valerianacece have 

 none of the essential characters of the Nyctaginacece ; for their ovary 

 is really inferior, the insertion of their perianth being what is called 

 epigynous. 2 The ovary of the Nyctaginacece on the contrary is quite 

 free and superior ; but it is constructed absolutely like that of 

 Piperacece and Urticaccce, that is to say, formed of one single 

 carpellary leaf inserted on the side of the axis which bears one single 

 ascending ovule. However, the ovule of the Nyctaginacece, always 

 reflexed and not orthotropous, distinguishes them clearly from the 

 Piperacece, which have neither their petaloid perianth nor their 

 embryo external to the albumen, but possess a double albumen. 

 The gynaeceum of Nyctaginacea is however also constructed like 

 that of the unicarpellary Phytolaccacece, that is to say, the Rivinece. 

 These last have also a farinaceous albumen enveloped by the 

 embryo ; and they are only distinguished by the organization of 

 their perianth, which has no inferior persistent thickened part, to 



1 S. Watson, in Unit. St. Geogr. Xxpl. of perianth, and its superior part to a corolla, is 

 fourt. par., Hot., 286, Jlermidium, n. 8, t. 32. quite in idmissible. The affinity appealed to in 

 Flowers in capituliform racemes, with 5-7 Pisonia and Vthwrmm is only due to superficial 



stamens, analogous to those of Mirabilis. appearances. The unicarpellary Thymelacea are 



2 The idea which A. L. DE Jussieu had of only distinguished from the Nyctaginacea! in the 

 comparing a calyx to the persistent part of the Hower by the direction of the ovule. 



