Oil the State of Vegetation on high Mountains. 271 



attain sooner or later to the year favourable to the matura- 

 tion of the seeds from which they are to be renewed. 



At Neouvielle, at an elevation greater by 250 metres than 

 thar of the Pic du Midi, and at which the thermometer 

 rises in summer only to 8 degrees, I collected, during five 

 excursions, twelve species, all vivacious. 



On the summit of Mount Perdu, at the absolute eleva- 

 tion of 35GO metres, in the bosom even of the permanent 

 snow, but under rocks freed^ from it by the inclination of 

 their sides, I collected six species exceedingly vigorous. 

 Here on one of the warmest days of a year remarkable for 

 its heat, the thermometer rose only to 5-5°, above the freez- 

 ing point, and it no doubt descends in winter to 2.5°- and 

 30°; and is it certain, that the plants which 1 foand here 

 uncovered, in a year when the snow had undergone an ex- 

 traordinary diminution, disengage themselves from it every 

 year ? Beside?, I have seen some reappear, which existing on 

 the edge of the permanent snow, remain almost always bu- 

 ried under its extension: they do not see the light perhaps 

 ten times in a century, and then they pass through the 

 circle of vegetation in the short "space of some weeks, to 

 sleep again during a winter of several years. It cannot be 

 expected that plants subject to conditions of existence so 

 singular should be found among the number of the species 

 which we observe in the plains of our temperate climates : 

 they belong either exclusively to the highest summits of the 

 mountains, or jhey are represented merely in the polar 

 countries of Europe. Norway, Lapland, , and Greenland 

 are countries which furnish plants analogous to those 

 which grow on the summit of the Alps and the Pyrenees; 

 they arc not found in Siberia or Kamschatka, nor in the po- 

 lar countries of America^ though it is as difficult to conceive 

 the diversity which prevails among the vegetable produc- 

 tions of countries so similar and so near to each other, as it 

 is difficult to explain the conformity which exists between 

 the vegetation of one of them ar.d that of the summits of 

 some mountains which are 40 degrees distant from them. 



But we are informed by observation that the propagation of 

 vegetables does not always take place parallel to the equator; 

 that if a certain number of plants confined by their tempe- 

 rament to a determinate climate are found at some distance 

 under the same latitudes, many others, on the contrary, 

 seem to have been carried away in the direction in which 

 our continents separate, and to be dispersed in the direction 

 of the meridians. On the south, America, Africa, and 

 Asia; on the north, Europe, A*ia, and America, are far 

 4 from 



