NATURAL OKIJEKS. 143 



In other intratropical countries tlic proportion may be still 

 smaller ; but I can neither adopt the general equinoctial im 

 ratio given by Baron Humboldt, namely, that of 1 : 00, 

 nor suppose with him that the minimum of the order is 

 within the tropics. For Cyperaceae, like Rubiaceae, and 

 indeed several other families, is composed of tribes or ex- 

 tensive genera, having very diflerent relations to climate. 

 The mass of its equinoctial portion being formed of Cyperus 

 and Fimbristylis, genera very sparingly found Ijeyond the 

 torrid zone ; while that of the frigid and part of the tempe- 

 rate zones consists of the still more extensive genus Carex, 

 which hardly exists within the tropics, unless at great 

 heights. Hence a few degrees beyond the northern tropic, 

 on the old continent at least, the proportion of Cyperaceae 

 is evidently diminished, as in Egypt, according to ^I. 

 Delile's valuable catalogue ;^ and the minimum will, I be- 

 lieve, be found in the Flora Atlantica of M. Desfontaines 

 and in Dr. Russel's catalogue of the plants of Aleppo." It 

 is not certain, however, that the smallest American pro- 

 portion of the order exists in the same latitude. And it 

 appears that in the corresponding parallel of the southern 

 hemisphere, at the Ca])e of Good Hope and Port Jackson, 

 the proportion is considerably increased by the addition of 

 genera either entirely different from, or there more extensive 

 than, those of other countries. 



Among the Cyperaceae of the Congo herbarium there 

 are fifteen species of Cyperus, of which C. Fapjiii's appears 

 to be one. The abundance of this remarkable species, 

 especially near the mouth of the river, is repeatedly noticed 

 in Professor Smith's journal, but from the single specimen 

 with fructificalion in the collection, its identity with the 

 plant of Egypt and Sicily, though very probable, cannot be 

 absolutely determined. I perceive a very slight ditfereucc 

 in the sheaths of the radii of the common umbel, Avhich in 

 the plant from Congo are less angular and less exactly 

 truncated, than in that of Egypt ; in other respects the two 

 plants seem to agree. I have not seen C. laxifiorus, a 



^ Flor. ^Egi/pt. Illustr. in Descrip. de VEgypte, Uist. Xat. 2, p. 49. 

 ' Nat. Hist, of Aleppo, 2/id ed. vol. 2, 7;. 242, 



