RUTACEÆ. 441 
case with all the Quassiee, Cuspariee, and Aurantiee ; some are en- 
tirely American, others are Asiatic and Oceanian. We have seen 
that Diosmeæ is only found in South Africa, and Boroniee in Oceania. 
Zanthoxyleæ is met with in all the warm regions ; in the temperate 
regions we only observe a few species of Zanthroxylon, Phelloden- 
dron, which is found in North-east Asia, and Pfe/ea, a native of North 
America. Swriana, a plant found near the sea, has been met with on 
all the tropical sea-coasts. Rutee and Zygophylleæ often belong to 
cooler climates. Thus in Europe we meet with the genera Ruta, 
Dictamnus, Tribulus, Zygophyllum, Fagonia, and Peganum. The genus 
Cneorum is also represented there. Only six genera are common to 
the two Worlds; forty properly belong to the New World. The 
other genera belong especially to the Old, as do also all the Diosmee, 
Boroniee, Aurantiee, Balaniteæ, Cneoree, and Nitrariee. The number 
of species hitherto described, and which may be considered as dis- 
tinct, are about nine hundred and twenty, of which only two hun- 
dred and sixty are American; that is to say, more than two-thirds 
belong to the Old World. 

The affinities of such a group must be many. By Zygophyllee it 
is nearly allied to Geraniee, from which Zygophyllee only differ by 
the leaves, the absence of a fragrant oil, the mode of organization 
of the fruit, and the way in which the carpels of the Geraniee sepa- 
rate at maturity from the central columella. The Biedersteinice, 
which have been really connected with the Geraniaceæ, are, on the 
other hand, closely allied to Swrianee ; they only differ by their 
entire and punctuate leaves, by the presence in each ovary of 
Biebersteinia of a single ovule, while there are two in Swriana, where 
they are, like the seeds, constructed in a peculiar manner. By 
Suriana, Rutacee is also closely connected with the Ochnacee, which 
are, as we have seen,' scarcely separable from Quassie and Zanthorylee. 
We must search much further to find a connexion between the 
Quassias and the genus Crossosoma, which is an abnormal Ranuncu- 
lacee,(?) but having the perianth, free carpels, and bitterness of 
Quassia, from which it only differs by its stamens, indefinite in num- 
ber, and its arillate seeds ; it is the same with the genus Rigiostachys, 
allied to Ochnaceæ, Connaraceæ, Surinaceæ, and Rosacee, with one of 
} See p. 365. 
