MINOR VEGETABLE PRODUCTS AND THEIR souRCcES. 171 
altered conditions, but experience seems to prove that no permanently 
useful result has been obtained by this course. Individual plants may 
be influenced, to a certain extent, by local causes of soil and climate; 
but the capacity of a species to resist heat or cold, aridity or moisture, 
remains unaltered. This is well exemplified in the case of the tomato, 
which, although it has been cultivated for one hundred years, and 
generation after generation has been raised from its seeds, is still as 
easily affected by cold as it was when first introduced into cultivation. 
The external appearance of a plant affords but. little assistance in 
determining its climatic nature. There are, however, certain observable 
features that may be noticed. Plants having an abundance of expansive 
foliage, as some palms, musas, &c., are natives of a humid atmosphere. 
Asiatic plants have been noted for their beauty; African, for their 
fleshy and succulent leaves, as the aloes and mesembryanthemums; 
American, for the smoothness and length of their foliage, and for the 
singularity of shape of their flowers and fruit. Plants indigenous 
to polar and mountainous regions are generally low, with small and 
compressed leaves, but with flowers large in proportion. Austzalian 
plants are distinguishable for small, dry, and shriveled leaves. In. . 
Arabia they are low and dwarfish ; in the Indian Archipelago generally 
shrubby and furnished with prickles; while in the Canary Islands 
many, which in other countries are merely herbs, assume the appear- 
ance of shrubs and trees. The shrubby plants of the Cape of Good 
Hope and Australia exhibit a striking similarity, as do also the shrubs 
and trees of the northern parts of Asia and America, which may be 
exemplified in the Platanus orientalis of the former, and in the Platanus 
occidentalis of the latter, as well as in the Fagus sylvatica and Fagus 
ferruginea, or Acer Cappadocium and Acer saccharinwm, and yet the herbs 
and undergrowth of the two countries are very dissimilar. 
A knowledge of the native country of a plant is not always sufficient 
information regarding its powers of endurance. The mere fact that a 
plant is a native of China, or that it comes from South America, will 
not in itself enable us to assign a limit to its climatic range; as we 
have plants from both these countries which are capable of resisting a 
zero cold, while we have others from the same places which would be 
killed if subjected to a temperature of 32°. Temperature is the grand 
regulating condition, and as this is affected by elevation as well as by 
increase of latitude, we find the mountain ranges near the equator pre- 
senting all the features of a tropical, a temperate, and even an arctic 
vegetation. Thus palms and plantains luxuriate at the bases of these 
tropical mountains. Above these appear oranges and limes; then 
sneceed corn and wheat; and still higher commences the series of 
plants peculiar to temperate regions. Similar phenomena present them- 
selves in temperate latitudes. ‘‘ We may begin the ascent of the Alps, 
for instance, in the midst of warm vineyards, and pass through a suc- 
cession of oaks, sweet chestnuts, and beeches, till we gain the elevation 
of the more hardy pines and stunted birches, and tread on pastures 
fringed by borders of perpetual snow. At the elevation of 1,950 feet 
the vine disappears; and at 1,000 feet higher the sweet chestnut ceases 
‘to thrive; 1,000 feet farther up, and the oak is unable to maintain itself; 
at an eluvution of 4,680 feet.the birch ceases to grow; and the spruce 
fir at the height of 5,900 feet, beyond which no tree appears. The 
Rhododendron ferrugineum then covers immense tracts to the height of 
7,800 feet, and the herbaceous willow creeps 200 to 300 feet higher, 
accompanied by a few saxifrages, gentians, and grasses, while lichens 
and mosses struggle up to the imperishable barrier of eternal snow.” 
