INTRODUCTION. 



7 



shade, if the enormous masses of foliage causing it had not been placed and 

 arranged by provident Nature in such a manner as to permit the solar rays, though 

 broken in a thousand ways, to penetrate with sufficient force to the lower vege- 

 tation ? Our pine woods do not require a similar provision ; their darkest shade * 

 falling on a soil which, having nothing to produce save the trees, can dispense 

 with the influence of light, though the trees themselves do require protection 

 against violent winds and heavy masses of snow, the melting of which is so much 

 assisted by being distributed over the broad branches. 



These very different modes of life must necessarily produce very different 

 aspects. In a climate where the plants never suffer from the cold, they display a 

 certain freedom looked for in vain in regions subject to great changes of tempe- 

 rature, and where trees and shrubs, developing a vast number of small branches, 

 form perhaps thicker but on the whole poorer crowns. This is seen in most Alpine 

 plants in a much higher degree, especially those growing gregariously, the leaves 

 of which are not only placed close together, but also pressed close to the ground : 

 the cold, it would appear, totally restricting the upward extension of the branches. 

 This is most marked on tropical mountains, where one has only to descend into 

 the plains in order to behold the very opposite character of the vegetation already 

 mentioned. The peculiarity of a vegetation always enjoying a warm and moist 

 atmosphere is particularly evident in the elegant forms of palms and tree-ferns, 

 constituting, in reality, the type peculiar to most tropical zones. In that climate 

 we behold not only in the Yuccas, Dracmnas, screw-pines (Pandanus), large 

 Scitamineous plants, &c, a surprising repetition of the chief features of the 

 palms, but to a certain extent even the external branches and spreading leaves 

 of the largest forest trees form crowns not unlike those of palms on a small 

 scale. If the crowns often consist of heavy and undivided leaves, and thus again 

 differ from palms, the Mimosa-form, playing so important a part in the tropics, 

 steps in, and by its delicate feathery foliage imitates the features of a palm in a 

 surprising degree. There are even mimosa-like trees which assume a much more 

 palm-like look than one would be prepared to expect in a dicotyledonous plant. 

 Everywhere in that climate one observes a certain quite peculiar kind of (( trellis- 

 work,"! if it may be so called, the most highly developed in the palms, and 

 even in plants which can be but little compared to them, and probably owe their 

 prevailing character to the free development they enjoy. Grreat masses of delicate 



* " Juniperi gravis umbra, nocent et frugibus meaning ; but it is the nearest English equivalent 

 umbrae." Virg. Eel. X. I could find for the German " Durchbrochenheit." — 



f This term does not quite express the author's Berthold Seemann. 



B 4 



