proportion, however, in equinoctial Africa would be the more remarkable, as there is probably no part of the world in which Compositæ form so great a portion of the vegetation as at the Cape of Good Hope.
RUBIACEÆ. Of this family there are forty-three species in the collection, or about one fourteenth of its Phaenogamous plants. I have no reason to suppose that this proportion is greater than that existing in other parts of equinoctial Africa; on the contrary, it is exactly that of Smeathman's collection from Sierra Leone.
Baron Humboldt, however, states the equinoctial proportion of Rubiaceæ to phænogamous plants to be one to twenty-nine, and that the order gradually diminishes in relative number towards the poles.
417] But it is to be observed that this family is composed of two divisions, having very different relations to climate; the first, with opposite, or more rarely verticillate, leaves and intermediate stipules, to which, though constituting the great mass of the order, the name Rubiaceæ cannot be applied, being chiefly equinoctial; while the second, or Stellatæ, having verticillate or very rarely opposite leaves, but in no case intermediate stipules, has its maximum in the temperate zones, and is hardly found within the tropics, unless at great heights.
Plence perhaps we are to look for the minimum in number of species of the whole order, not in the frigid zone, but, at least in certain situations, a few degrees only beyond the tropics.
In conformity to this statement, M. Delile's valuable catalogue of the plants of Egypt[1] includes no indigenous species of the equinoctial division of the order, and only five of Stellatæ, or hardly the one hundred and sixtieth part of the Phænogamous plants. In M. Desfontaines' Flora Atlantica, Rubiaceæ, consisting of fifteen Stellatae and only one species of the equinoctial division, form less than one ninetieth part of the Phænogamous plants, a proportion somewhat inferior to that existing in Lapland.
- ↑ Flor. Egypt. Illustr. in Descript. de l'Egypt, Hist. Nat. v. 2, p. 49.
