INFLUENCE OF CLIMATE ON VEGETATION. 
295 
states of artificial climate — are totally inefficient towards the successful culture of those 
numberless exotic forms of vegetation which require a higher temperature than our climate 
naturally affords. Our aim is, that the fact thus acknowledged in practice, may also 
become fixed in the language of horticulture. 
We set out by asserting that the two old divisions, “ stove ” and “ greenhouse,” are 
inadequate, and that more groups must be formed ; but it is not necessary to carry the 
subdivision to an opposite and inconvenient extreme. Probably the formation of zones 
corresponding to every 10° of mean annual temperature above that of England, would 
indicate nearly all the divisions into which tender cultivated plants would require to be 
separated. Thus we shall have formed the following groups ; the two latter of which 
would represent all subjects, hardy as respects temperature, in the southern and midland 
parts of Great Britain. 
The Equatorial Group = 
The Tropical and Sub-tropical Groups = 
The Warmer Temperate Group = 
The Temperate Group = 
The Sub-Temperate Group = 
The Polar Group = 
The Tropical and Sub-tropical Group would 
Mean Temp. 80° — 90° 
„ 70°— 80° 
„ 60° — 70° 
„ 50° — 60° 
„ 40° — 50° 
„ 32° — 40° 
probably require sub-division. 
Fah. 
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Any scheme of this kind, it must be remembered, will be of necessity arbitrary, and 
liable to objections, which it may be expected will from time to time arise. Thus, at the 
outset, we find that the two last-named of the above groups represented by the range of 
mean temperature 32° — 50°, and which are assumed to correspond to plants hardy in 
the climate of England, are, at the highest point, somewhat below the mean temperature 
assigned to London, which is 51°. This slight discrepancy will not however be found to 
materially affect the result ; the temperate plants, represented by 50° — 60°, not differing 
so much from those below them in requiring greater heat, as in their not enduring with 
impunity so considerable an amount of cold. 
We shall now sketch out briefly the zones with which the above-named groups are 
intended to correspond, leaving altitude out of consideration for the present. 
Mean Temp . : 80° — 90°. The equatorial zone does not exactly correspond to the true 
equator. Commencing a circuit in the Pacific Ocean, it lies entirely on the southern side 
of the line, takes in the Galapagos group of Islands lying on the equator towards the 
American Coast, and then passing suddenly to the north of the line, takes in Panama, New 
Granada, Venezuela, and the Barbadoes group of Islands. Then turning northwards, 
it crosses the Atlantic, taking again a northerly direction, and including a portion of Africa 
entirely on the north of the line, its northern limit striking the African Coast about the 
10° of lat. passing diagonally to 20°, and then extending nearly parallel with the equator 
to the Arabian shores in the Indian Ocean. In this tract is comprehended Guinea, 
Soudan, Nubia, Abyssinia, and the northern portion of Arabia with the Island of Socotra. 
The zone then crosses the Indian Ocean to the shores of India, where leaving Bombay to 
the north, it crosses the Bay of Bengal, taking in Madras, including also Ceylon. Here its 
southern boundary crosses the line, but so that it takes in the Malay Peninsula, and the 
Islands of the Eastern Archipelago, exclusive of Java and some other small Islands on the 
same parallel, together with a small slice of New Guinea in the southern hemisphere, and 
the Philippines in the northern. 
Mean Temp.: 70° — 80°. The northern tropical and subtropical zones take in the 
Sandwich Isles in the Pacific, whence their northern boundary crosses Lower California 
about Santa Margarita, then to Cingaloa on the Mexican coast across Mexico, taking in 
of course Guatemala, skirting the northern side of the Gulph of Mexico, and including 
Florida, with the islands of Cuba, Jamaica, Hayti, and the rest of the Bahamas and West 
Indian group. In the Atlantic they include the Cape de Verd group, which lie towards their 
southern, and the Madeira group, near their northern limit ; then crossing Africa, they 
take in Senegambia, the Great Sahara, Egypt, Arabia, Persia, the remaining part of 
Hindoostan, Birmah, Siam, Tonquin, and as far north as Fou-tchou, in China, together 
with the Island of Formosa, the Philippines, and the Marianne Isles. 
