366 Prof. Schou w on the Geographical Distribution of the Vine . 
spring and autumn, must prevent the culture of the vine, 
however high the summer temperature may be. Frequent 
night frosts, at the time when the leaves are unfolding, or when 
the blossom shews itself, and a low temperature in the autumnal 
months, in which the grapes come to their full maturity, must 
act injuriously on the vine. Perhaps there is here a concomitant 
reason why, in North America, the vine does not ascend farther 
to the north, although the summer temperature is high in pro- 
portion to the mean throughout the year. 
As the northern limit is chiefly determined by the medium 
temperature of summer, it is equally so with the southern. In 
Madeira and the Canary Islands, the mean temperature is not 
much lower than in Algiers or Cairo, and yet the culture of the 
vine is very considerable in these islands ; whereas in Algiers 
the temperature is already too high ; and in Cairo it is only 
planted for the sake of its shade. In islands, however, the sum- 
mer heat is lower than in continents. 
It is still more difficult to determine the natural than the ar- 
tificial distribution of the vine, or, what is the same, the coun- 
tries where it is a native. Every cultivated plant easily be- 
comes wild, and it is therefore often difficult to decide whether 
at any given place it may have been native. It is easy to shew, 
however, that the vine is not originally wild in the New Conti- 
nent, on the Canary Islands, Madeira, or the Cape. It is far- 
ther probable, that this also applies to all the countries of Eu- 
rope, on this side of the great Alpine range. In Caucasus and 
the Levant it frequently occurs wild, and every thing concurs 
to point out this as its original home. In the south of Europe 
this is more doubtful. It is indeed found in Italy, particularly 
in the southern parts, in woods, and in such circumstances that 
there one might be inclined to regard it as originally wild. I 
cannot, however, affirm this to be altogether ascertained. His- 
torical accounts, and popular traditions, might, perhaps, throw 
light upon the migrations of this plant. This investigation, 
however, does not properly belong to our subject. 
Within the limits of the vine, wine is the customary drink. 
In higher latitudes, beer and cider supply its place, and, as a 
spiritous drink, ardent spirits from grain. In the torrid zone, 
various plants afford substitutes for wine : thus, in Mexico, 
the Agave Americana is cultivated, and yields a kind of wine ; 
