SAPIXDACEJE. 



355 



and grecu, like tbo sepals, while the inner are large, membranous, 

 and coloured like the petals. Its flo\yers are dioecious and apetalous. 

 The Thohin/'ds constitute a small group of genera with regular 

 flowers, provided with petals, anda circular disk exterior to thestamons, 

 like those of 3IeUcocca, but whose uniovulate ovary cells become 

 so many samaras with superior dorsal wing, like those of the Maple, 

 separating at maturity. Such are : the Thouinias, plants from 

 tropical America, whose calyx is short, valvate, or hardly imbricate ; 

 the Atalaijas, shi'ubs from Oceania, whose sepals are large and 

 imbricate ; and Ptwroxylon (fig. 366-369), a tree from southern 



Pldsroxijlon utile. 



\ A 



3G6. Flower. 



Fig. 368. Seed. Fig. 369. Longi- Fig. 367. Longitudinal 

 tiidinal section of seed. section of flower. 



Africa, whose flowers are tetramerous, with a disk interior to the 

 stamens, instead of being exterior to them, like those of the pre- 

 ceding genera, and whose fruit is formed of two samaras, each 

 dehiscing in two valves and containing a seed prolonged upwards in 

 a long membranous wing placed between the two plates of those of 

 the fruit. In all these genera, the ovule, solitary in each cell, is 

 ascendent, with exterior micropyle. 



The Dodonwas have given their name to a small group, not very 

 natural, and which we do not think should be distinguished witli 

 the title of tribe or scries, but which is easily recognised in 

 practice, by its ovary cells each containing two ovules, usually 

 (though not constantly) obliquely descendent, when the micropyle 

 is exterior and superior. They are both primitively so in the 

 Mclicopsidium, a shrub lately discovered in New Caledonia, having 

 the aspect and trifoliate leaves of certain llulaeece, and regular 

 flowers with five imbricate sepals, five large imbricate petals, with 



