682 ZONES AND REGIONS [Pt. Ill, Sect. Ill 



when compared with those of vegetative shoots, are often very considerable. 

 Yet in the arctic flora it appears that there are not wanting species the 

 formation of whose flowers is dependent on higher temperatures. Thus, 

 according to Kihlman, the majority of dwarfed Coniferae beyond the tree- 

 limit have no cones ; Rubus Chamaemorus is without flowers at its most 

 northern station. 



In certain cases the temperatures suffice for the formation of flowers, but 

 not for that of fruits and seeds, which require a higher temperature. Thus, 

 at the tree-limit many Coniferae still produce cones ; but these to a great 

 extent are sterile. Owing to the early flowering, however, fruits and seeds 

 mostly develop during the warmest season, so that a large number of them 

 frequently ripen 1 . 



The increased intensity of colour in arctic flowers mentioned in most 

 books of travels is usually and correctly explained as an effect of prolonged 

 illumination 2 . Other substances, such as ethereal oils, the formation of 

 which is also favoured by light, are rare ; scented flowers are confined to the 

 few orchids that do not go far north, and to Ranunculus Pallasii ; aromatic 

 vegetative organs are also rare. 



vi. REPUTED PROTECTIVE MEASURES AGAINST COLD. 



As we find it very cold in the extreme north and require very imperme- 

 able clothes, we are apt to imagine that plants experience the same need. 

 Hence, formerly, even by Grisebach, all peculiarities of polar vegetation 

 were correlated with the cold. One may here well abstain from criticizing 

 the entirely hazy physiological concepts which Grisebach entertained 

 regarding the effects of cold. 



Kjellman early recognized that arctic vegetation appeared to be exposed, 

 without adequate protection, to the action of cold. In opposition to pre- 

 vailing ideas, he showed that the epigeous parts of plants usually exceed 

 in volume those that are hypogeous, and that the latter are also exposed 

 to the lowest temperatures. He showed what exaggerated ideas prevailed in 

 regard to the protection that snow affords against cold, especially when, as 

 is usually the case, only a thin layer of snow is in question 3 . He negatived, 

 in most cases, the existence of a bud-protection for the hibernating parts, 

 and, where such existed, he showed that it appeared to be not more elabo- 

 rate than in more southern zones. The same is true in regard to hairs, which 

 were frequently considered as affording protection against the cold, but which 

 are neither more frequent nor more abundant than in temperate Europe. 

 As a specific protective contrivance against cold Kjellman recognizes only 

 ' the occasionally very thick covering of wilted dry leaves and remains of 



1 Kjellman, op. cit. 2 See Schuebeler, op. cit. ; Bonnier and Flahault, op. cit. 



3 Kjellman, op. cit., p. 699. 



