PL A TEA UX OR MONT A NE FL OR A . 151 



During the colder part of the glacial period, when L.ebanon maintained 

 glaciers to about 4,000 feet below the summit, and the Jordan Valley was 

 most likely a series of lake-basins, all, including the Dead Sea, much 

 more extensive than at present, the climatic condition of Sinai must have 

 been about equivalent to that of the British Isles at the present period, 

 with an abundant rainfall, and the then alpine flora of Lebanon may 

 perhaps have extended to Sinai. It is reasonable to infer that Lebanon 

 has had a more plentiful alpine flora than the very few existing remnants 

 would seem to imply. Mountains in the Himalayan region at similar 

 altitudes and further south are far better stocked with Arctic species. Sir 

 Charles Lyell, commenting on this southern extension of the glacial 

 severity to Lebanon, first noticed by Sir Joseph Hooker, thinks it pro- 

 bable that it is referable to the earliest portion of the ' great ice age,' in 

 which case the Arctic species that must have once decked the upper 

 heights of Lebanon have had all the greater time to perish. Although 

 at present the snow never quite leaves the summits of Lebanon and 

 Hermon, the summer atmosphere is drier and warmer than an alpine 

 flora would thrive under ; on the barren Sinaitic mountains this , is, of 

 course, still further the case. 



At this period no doubt Sinai was abundantly vegetated. The more 

 temperate northern and north-eastern floras were pushed southwards by 

 the northern cold, their predecessors being either exterminated, so far 

 as Sinai is concerned, or, if allowed sufficient time, highly modified or 

 driven south in their turn along the adjoining continents. As milder 

 influences began to prevail more and more, Arabian forms crept in ; 

 the connection of Sinai with that country across the Arabah watershed 

 remaining unsevered. Finally, when the glacial period mollified, and the 

 temperate forms retired upwards, the Arabian flora steadily advanced 

 northwards from the south of its peninsula, and overran the lower parts 

 of Sinai. With the elevation of the Sinaitic peninsula, and a gradual 

 more or less lagoon-divided connection with Africa, corresponded an 

 increased temperature, and Nubian and other African forms also spread 

 northwards, and finally eastwards. At the same period, and subsequently, 

 a great portion of the present flora of the Delta obtained its opportunity 

 for extending westwards, and hence the number of Arabian forms which 

 occur in Lower Egypt. This elevation must have continued until it 



