390 Observations on the geographical Extension 



distinctions ; and, although the cultivation from seed and cuttings 

 succeeds very well in European gardens, the peculiarity of the 

 species cannot with certainty be preserved. Whoever has seen 

 the Cacti in their native country, and has observed the truly 

 wonderful and grotesque character which they assume as a 

 feature in the landscape, and has also observed their inclination 

 to sport in our gardens, will not oppose the above statement. 

 Such an enquiry into the difference of the species seems par- 

 ticularly necessary with regard to the genus Opuntia, because 

 botanical writers know but little of them in their native country. 

 It is possible, certainly, that many species of this genus, such 

 as Opuntia spinosissima, Tuna, polyantha, elatior; JFicus indica 

 and vulgaris ; and several species of Cereus, such as C. triangu- 

 laris, trigonus, quadrangularis, and pentagonus, may have the 

 most extensive localities : at least I have observed them under 

 different latitudes in Brazil, and in different localities ; and they 

 were introduced into our gardens, before all the others, from the 

 Antilles. 



The Cacti require a dry, little variable, warm, and even hot 

 climate, and a clear and almost unclouded sky. Such a climate 

 as this is called in Brazil mimoso. These plants are therefore 

 found in abundance in open plains, where there are no evergreen 

 forests ; but which are covered either with low bushes, leafless 

 during the droughts of summer, or with small plants. We 

 must not, therefore, look for the Cacti in forests which have a 

 warm and damp climate; as their cool shade is as little fa- 

 vourable to the Cacti, so eager for the light, as it is for the 

 Agave, which is never found in such places, and is therefore 

 erroneously so placed by artists in their views of tropical forests. 

 According to my observations, the Cacti are found on very 

 different kinds of stone ; and perhaps it is not so much the che- 

 mical formation of the soil, as the situation and temperature, 

 which insures their successful growth. In Peru and Mexico 

 they are frequently found on porphyry and many trap formations, 

 and also on hard lava. In Brazil, I have seen them on granite, 

 chalk, quartz, and mica slate, and more rarely on clay and 

 chlorite slate, the latter of which appears to be less favourable to 

 their vegetation than the others mentioned. They prefer a hard 

 stony sandy soil or the crevices of rocks, to a light soil or rich 

 loamy earth. Open, sunny, warm situations, on which even 

 grass and other low plants can hardly grow, are often thickly 

 covered with Cerei and Opuntia?, and Mammillariae; Echino- 

 cacti and Melocacti are frequently found, like our houseleek, on 

 perfectly naked rocks. The PereskzVe alone, which, from the 

 nature of its leaves, announces that its respiration is more 

 analagous to other plants, is found under trees and shrubs, and 

 forms an excellent natural hedge, whereas the Opuntia requires 

 to be planted when used for the same purpose. 



