Chap. II] REGIONS OF VEGETATION 719 



H. Meyer found a few lichens on the summit of Kilimanjaro (6,010 m.), 

 and it is probable that this point by no means represents the uppermost 

 limit of vegetation. Bacteria in particular would appear to ascend still 

 higher. 



It is much easier to fix the upper limit of phanerogamic vegetation. 

 The highest known station for phanerogams is not in the tropics, but 

 in West Tibet, where at 5,800 m. Saussurea tridactyla (Fig. 41 8, A) 

 grows. This flowering plant that ascends highest of all does not display 

 the alpine habit to a particularly marked extent, as its axis grows up to 

 the relatively considerable height of about 15 cm. It is protected against 

 transpiration by a massive coat of woolly hairs. The alpine habit is 

 exhibited to a higher degree in some species of the same genus, which 

 inhabit the same mountains as S. tridactyla, yet do not reach the highest 

 station, but grow between 5,000 and 5,500 m. (Fig. 418, B-D). 



The lower limit of perpetual snow does not by any means mark the 

 upper limit of plant-life, not even that of flowering plants, isolated indi- 

 viduals of which occur in the Swiss Alps at about 4,000 m. 



SELECT LITERATURE. 



Battandier, A. Quelques mots sur les causes de la localisation des especes. Bulletin 

 de la Societe botanique de France. Tome XXXIV. 1887. 



Bonnier, G. I. Cultures experimentales dans les hautes altitudes. Comptes ren- 

 dues de l'Academie des sciences de Paris. Tome CXX. 1890. 



II. Influence des hautes altitudes sur les fonctions des vegetaux. Ibid. 



III. Etude experimentale sur rinfluence du climat alpin sur la vegetation et 



les fonctions des plantes. Bulletin de la Societe botanique de France. Tome 

 XXXV. 1888. 



IV. Etudes sur la vegetation de la vallee de Chamonix et de la Chaine du Mont 



Blanc. Revue generale de botanique. Tome I. 1889. 



V. Les plantes arctiques comparees aux memes especes des Alpes et des 



Pyrenees. Ibid. Tome VI. 1894. 



VI. Recherches experimentales sur 1'adaptation des plantes au climat alpin. 



Annales des sciences naturelles. y e serie. Tome XX. 1895. 



VII. Cultures experimentales dans les Alpes et les Pyrenees. Revue generale 



de botanique. Tome II. 1890. 

 Bonnier, G., et Flahault, Ch. Observations sur les modifications des vegetaux 



suivant les conditions physiques du milieu. Annales des sciences naturelles. 



6 e serie. Tome VII. 1878. 

 Christ, H. Das Pflanzenleben der Schweiz. Zurich, 1879. 

 Dodel-Port, A. Farbenpracht und Grosse der Alpenblumen. Kosmos. Bd. I. 



1879. 

 Heckel, Ed. Sur l'intensite du colons et les dimensions considerables des fleurs aux 



hautes altitudes. Bulletin de la Societe botanique de France. Tome XXX. 



1883. 



