458 APPENDIX. No. V. 



can neither adopt the general equinoctial ratio given by Bai-on Humboldt; 

 namely, that of 1 :60, nor suppose with him that the minimum of the order is 

 mtliin the tropics. For Cyperaceae, like Rubiaceae, and indeed several other 

 families, is composed of tribes or extensive genera, having very different rela- 

 tions to climate. The mass of its equinoctial portion being formed of Cyperus 

 and FimbristyUs, genera very sparinglj- found beyond the torrid zone ; while 

 that of the fi-igid and part of the temperate 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 M. Delile's valuable catalogue ;* and the minimum will, I believe, 

 be found in the Flora Atlantica of M. Desfontaines and in Dr. Russel's 

 catalogue of the plants of Aleppo.-f- It is not certain, however, that the 

 smallest American proportion 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, tlie proportion is considerably 

 increased by the addition of genera either entirely different from, or there 

 more extensive than those of other countries. 



Among the Cyperacea 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 tlie 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 ai-e 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 species discovered in Madagascar by M. du Petit Thouars, and said to 

 resemble C. PapjTus except in the vaginae of the partial umbels.:|: 



Among the species of Cyperaceae in the collection, having the most extensive 

 range, are Cyperus articulatus, which is common to America, India, and 



* Flor. jEgypt. Jllustr. in Descrlp. de I'Egypie, Hist. JVat. 2, p. 49. 

 t Nat. Hist, of Aleppo, 2rf. f rf. iwl. 2, p. 242. 

 X Encyc. Method. Botan. vol. 1, p. 270. 



