Chap. II] 



REGIONS OF VEGETATION 



709 



defloratus, Teucrium Scorodonia), than in the lowlands, and more intensely- 

 coloured. The histological structure exhibited a marked increase in protec- 

 tive contrivances against the loss of water : thicker cuticle, thicker and 

 earlier formation of cork, production of a hypoderma, lengthening of palisade- 

 cells, and, to judge by the illustrations, a reduction in the intercellular 

 spaces (Figs. 416, 417). Yet apparently the 

 number of stomata is increased, in particular on 

 the upper surface of the leaves. 



The shortness of the epigeous shoots in 

 the plants experimentally cultivated on the 

 Alps was due rather to a reduction in length 

 than to a reduction in number of the inter- 

 nodes, and was most striking in Helianthus 

 tuberosus, the tubers of which in a mountain 

 climate produced only basal rosettes of leaves ; 

 in cultures in the lowlands, however, they 

 produced normal tall shoots. But in general 

 the changes, even if well marked, were less 

 fundamental. Helianthemum vulgare (Fig. 415) 

 and Leontodon Taraxacum (Fig. 414) afford 

 typical examples. 



The alpine habit in Bonnier's mountain 

 cultures became stronger every year, and dis- 

 appeared in lowland cultures only in the course 

 of years. The mountain climate therefore, 

 besides its direct effects, has after effects, through 

 which we may explain the partially hereditary 

 nature of the alpine features of typical mountain 

 plants. As an example of the structural changes FlG 4II Alpine flora of New 

 caused by the mountain climate, the following Zealand A perennial rosette- 



. plant. Celmisiasessilinora,Hook. 



table is taken from Bonnier s paper l : — f. (Compositae). Natural size. 



Comparison of Plants of Trifolium repens grown in a Lowland and in 



an Alpine Climate. 



20th and 21st of April, 1889. 

 Cutting grown in Cadeac (Loivlands). 



Maximum size, 0-22 m. 

 Flowers less crowded, pedicel and calyx- 

 tube of about the same length. 



Cutting groivn on the Arbison Chain 

 (Mountains). 

 Maximum size, 0-13 m. 

 Flowers closely crowded together (less 



numerous in the umbel). Length of 



pedicel one-third to one-quarter that 



of the calyx-tube. 



1 Bonnier, VII, p. 543. 



