170 PHYSIOGNOMY OF PLANTS. 



and the same species the length of the leaves or needles 

 varies in the most striking manner from the influence of soil, 

 air, and elevation above the level of the sea. In travelling 

 in an east and west direction through eighty degrees of 

 longitude (above 3040 geographical miles), from the mouth 

 of the Scheldt through Europe and the north of Asia to 

 Bogoslowsk in the northern Ural and Barnaul beyond the 

 Obi, I have found differences in the length of the needles 

 of our common Fir (Pinus sylvestris) so great, that some- 

 times a traveller may be misled by the shortness and rigidity 

 of the leaves, to think that he has discovered a new species 

 allied to the Mountain Pine, P. rotundata (Link), P. un- 

 cinata (Ram.) Link has justly remarked (Linnsea, Bd. xv. 

 1841, S. 489) that such instances may be regarded as tran- 

 sitions to Ledebour's P. sibirica of the Altai. 



In the Mexican highlands I have looked with particular 

 pleasure on the delicate cheerful green of the Ahuahuete, 

 Taxodium distichum (Rich.), Cupressus disticha (Linn.), 

 which, however, is much given to shedding its leaves. In 

 this tropical region the above-mentioned tree, (of which 

 the Aztec name signifies water-drum, from atl, water, 

 and huehuetl, a drum, the trunk swelling to a great 

 thickness), nourishes 5400 and 7200 (5755 and 7673 Eng- 

 lish) feet above the level of the sea, while in the United 

 States of North America it is found in the low grounds 

 of the cypress swamps of Louisiana, in the 43d parallel. 

 In the Southern States of North America the Taxodium 

 distichum (Cypres chauve) reaches, as in the Mexican 

 highlands, the height of 120 (128 English) feet, and the 



