MOUNT RORAIMA IN BRITISH GUIANA, 5 
it descends presumedly into the forest-belt or to the base of the cliffs*. Roraima bears 
the most eastern patch of * tierra fria" upon the northern side of the Amazon. 
Some hundreds of feet above the commencement of the * tierra fria ” is the limit 
of trees. There are reasons for believing that both the Coast Andes and Roraima just 
reach this limit; they do not distinctly rise above it. 
The Flora.— Passing on to a consideration of the nature of the flora of Roraima I have 
given in the table on pp. 8-16 as complete a list as is now possible of the species found 
on the mountain above 5000 feet, and we have in it : 
239 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 (27:8 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 
endemie genera. "The law that mountains by their isolation and extension, as well as by 
their latitude, produce endemie 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 the 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 mauy 
orders. One of them—Heliamphora—has no kindred in South America, but belongs, 
like Cyrilla, 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 Ericacez 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 :— Hann (* Handbuch der Climatologie; Stuttgart, 1883, p. 152), after quoting Boussingault’s estimate for 
the Andes of the tropics that :57? C. in mean aunual 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 one 
may allow App 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, 609 at 5400, 53? at 7100, 47? at 8600, and 46^ at 8740 feet. The following are all the recorded 
observations of which I am aware :— 
— 
| 
| Night. | 6-8 a.m. Midday and afternoon. | 
Summit, Quelch in 1894 ........ | 47° E. | 49-52° F. 645 E. 
» D T eee | sisi | ree, 54° (in mist). 
About 7000 M. Appun ..........| 50° 
About 6400 ft., Quelch.......... 50° | 
About 5400 ft., R. Schomburgk ..| 52° | 
” D 5p Nk EE 48° | E 
At the base, R. Schomburgk...... 58° and below | — 67 { iu reis 
” an ` EE eee a 58^5 
s o» BROW QS sse d.d 59? 
», ., Boddam-Whetham Below 60* 
» s Ee 54? 
