SAPINDAOEJE. 



355 



and green, like the sepals, -while the inner are large, membranous, 

 and coloured like the petals. Its flowers are dioecious and apetalous. 

 The Thouinias constitute a small group of genera with regular 

 flowers, provided with petals, and a circular disk exterior to the stamens, 

 like those of Meltcocca, but whose uniovulate ovary cells become 

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

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

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

 the Afaht/aSj shrubs from Oceania, whose sepals are large and 

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



Ptasroxylon utile. 



Fig. 366. Flower. 



Fig. 368. Seed. Fig. 369. Longi- 

 tudinal section of seed. 



Fig. 367. Longitudinal 

 section of flower. 



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

 stamens, instead of beiug 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 m 

 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 Dodonceas have given their name to a small group, not very 

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

 the title of tribe or series, 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 

 Melicopsidium, a shrub lately discovered in New Caledonia, having 

 the aspect and trifoliate leaves of certain Rutacece^ and regular 

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



