MOUNT KORAI.MA IN BRITISH GUIANA. 



it descends presumedly into fehe forest-belt or to the base of the dills*. Roraima bears 

 t lie most eastern patch of " tierra fria " upon the northern side of tbe Amazon. 



Some hundreds of feel above the commencement of tbe "tierra fria" is the limit 

 of trees. There are reasons for believing that both the Coast Andes and Etoraima just 

 reach this limit; tbey do not distinctly rise above it 



The Flora. — Passing on to a consideration of the nature of the flora of Roraima 1 have 

 given in the table on pp. 8-16 as complete a list as is now possible of the species found 

 on tbe mountain above 5000 feet, and we have in it : 



2:5!) Spermatophyta, of which 121 (50'6 per cent.) are endemic. 



88 Pteridophyta, of which 16 (18'2 per cent.) are endemic. 



63 Bryophyta, of which 15 (23"8 per cent.) are endemic. 



11 Thallophyta, of which 3 (27'3 per cent.) are endemic. 

 The proportion of endemic Spermatophyta may seem large, but does not exceed that on 

 record for some of the mountains of Mexico. Of far greater interest is the number of 

 endemic genera. The law that mountains by their isolation and extension, as well as bv 

 their latitude, ]>roduce endemic genera, is illustrated by their number in the ranges of 

 Cis-equatorial South America ; thus, there are eleven among the Spermatophyta on 

 Roraima, and only two on the Coast Andes, which are comparatively small and not 

 isolated ; but I am aware of no fewer than thirty-six in tbe extensive Andes of Colombia, 

 including with them the Cordillera of Merida. 



The endemic genera of Roraima are enumerated on p. 7. They belong to as mauv 

 orders. One of them — Seliamphora — has no kindred in South America, but belongs, 

 like Oyrilla, to a North-American group ; all the rest have more or less close allies 

 in genera of the South-American continent. Ledothamnus, however, deserves further 

 remark because it is one of the very few Ericaceae with ericoid leaves which exist in the 

 New World. 



* This belief is based chiefly upon the nature of the flora. With regard to temperature the following may be 

 added: — Hanu (' Handbuch der C'limatologie,' Stuttgart, 1883, p. 152), after quoting Boussiugault's estimate for 

 the Andes of the tropics that ••37° C. in mean annual temperature is lost for every 100 metres ascended, and 

 Humboldt's for Mexico and Colombia of '53° C. for every 100 metres, adds : " as a general rule for the tropics ona 

 may allow '58° C. for the amount of heat lost in every 100 metres ascended." This is equivalent to -4° F. for every 



100 feet. As the mean annual temperature of Demerara is 81°, we obtain for Roraima these figures : 65° F. at 



4000 feet, 00° at 5400. 53° at 7100, 47° at 8600, and 40 at 8740 feet. The following are all the recorded 

 observations of which I am aware : — 



Night. 



6-8 A.M. 



Summit, Quelch in 1894 47° F. 



,, im Thurn .... 



About 7000 ft., Appun 50° 



About 6400 ft., Quelch 50 J 



About 5400 ft., R. Schomburgk . . 52° 



,, ,, ,, im Thurn 48° 



At the base, R. Schomburgk. ..... 58" and below 



i, ,• ,, oo o 



„ ,, Brown .... 



„ „ Boddam-Whetham . . i Below 60° 



„ „ Quelch < 54° 



49-52° F. 



62° 



59° 



Midday and afternoon. 



64°-5 F. 

 54° (in mist). 



87° (shade). 

 100° (sun). 



