34 PHYSIOGNOMY OF PLANTS. 



space of an hour, and the objects, which at first were 

 mistaken for a flock of small birds, proved to be small 

 agglomerations of straws or blades of grass. Boussingault 

 sent me some of the straws, which were immediately recog- 

 nised by Professor Kunth for a species of Vilfa, a genus 

 which, together with Agrostis, is very abundant in the 

 provinces of Caraccas and Cumana : it was the Vilfa tena- 

 cissima of our Synopsis Plantarum sequinoctialium Orbis 

 Novi, T. i. p. 205. Saussure found butterflies on Mont 

 Blanc, as did Eamond in the solitudes which surround the 

 summit of the Mont Perdu. When Bonpland, Carlos 

 Montufar, and myself, reached, on the 23d of June, 1802, 

 on the eastern declivity of the Chimborazo, the height of 

 18096 (19286 E.) feet a height at which the barometer 

 sank to 13 inches 11-^ lines (14.850 English inches), we 

 saw winged insects fluttering around us. We could see 

 that they were Dipteras, resembling flies, but on a sharp 

 ridge of rock (cuchilla) often only ten inches wide, between 

 steeply descending masses of snow, it was impossible to 

 catch the insects. The height at which we saw them was 

 nearly the same at which the uncovered trachytic rock, 

 piercing through the eternal snows, gave to ' our view, in 

 Lecidea geographica, the last traces of vegetation. The 

 insects were flying at a height of about 2850 toises (18225 

 E. feet), or about 2600 E. feet higher than Mont Blanc. 

 Somewhat lower down, at about 2600 toises (10626 E. 

 feet), also therefore within the region of perpetual snow, 

 Bonpland had seen yellow butterflies flying very near the 

 ground. According to our present knowledge the Mam- 



