ON CINCHONA. 
247 
According to Decandolle, no less than eight genera (includ- 
ing forty six species) have been confounded under the name 
of Cinchona: they are, Cinchona properly so called, Buena 
(called by some botanists Cosmibuena,) Remijia, Exostema, 
Pinkneya, Hymenodyction, Luculia, and Danais. The same 
authority also states that the first of these genera (Cinchona 
properly so called) is distinguished from the others by the 
following characters: — 1st. The stamina are entirely concealed 
within the tube of the corolla, and never project beyond it. 
2dly. The fruit consists of two cocci, or carpella, which adhere 
to the calyx; it has a septicidal dehiscence from below up- 
wards. 3dly. The seeds are erect, and imbricated on each 
other, from below upwards. 4thly. The limb of the caylx is 
toothed only to a third or half of its length, and is persistent 
at the summit of the capsule. Mr. David Don has also point- 
ed out another character by which some of the genera may be 
distinguished — namely the form of aestivation. Thus, in the 
genera Cinchona and Pinkneya, the aestivation is valvate. In 
Buena, Lasionema (a genus formed by Mr. Don, to include 
the plant formerly termed Cinchona rosea,) and Luculia, it is 
imbricated; in Exostema it is induplicate; and in Hymenodyc- 
tion it is plated. 
Species of Cinchona. — In botanical writings great discre- 
pancy exists as to the real number of species of this genus. 
Thus Humboldt makes eighteen ; Poiret twenty -four ; 
Sprengel fifteen; Lambert seventeen; and Decandolle sixteen. 
This has arisen partly from the confusion of genera, and partly 
from the difficulty of determining what are real species and 
what only varieties. Thus the shape of the leaves, which has 
been used by some botanists for the distinction of species 
cannot be relied on; and " whoever," says Humboldt, "deter- 
mines single specimens of dried collections, and has had no 
opportunity to examine or observe them in their native forests, 
will, as is the case with the Bronzonetta papyrifera, be led to 
discover different species by leaves which are of one and the 
same branch." Moreover, great uncertainty exists as to the 
species yielding the Cinchona barks, as 1 shall show when 
