NATURAL ORDEES. 143 



In other intratropical countries the proportion may be still 

 smaller ; but I can neither adopt the general equinoctial im 

 ratio given by Baron Humboldt, namely, that of 1 : 60, 

 nor suppose with him that the minimum of the order is 

 within the tropics. Por Cyperacese, like Rubiaceas, and 

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

 tensive genera, having very different relations to climate. 

 The mass of its equinoctial portion being formed of Cyperus 

 and Fimbristylis, genera very sparingly found beyond 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 Cyperacese 

 is evidently diminished, as in Egypt, according to M. 

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

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

 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 Cape 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 Cyperacese of the Congo herbarium there 

 are fifteen species of Cyperus, of which C. Papyrus 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 fructification in the collection, its identity with the 

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

 absolutely determined. I perceive a very slight difference 

 in the sheaths of the radii of the common umbel, which 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. laxiflorus, a 



' Mor. Mgypt. Illusii: in. Descrip. de I'llgypte, Eisi. Nat, 2, p. 49. 

 ' Nat. Hist, of Aleppo, %nded. vol, %,p, 2i2. 



