CHAPTER II 

 CLIMATIC ZONES 



Latitude, as might be expected, plays a very important role in 

 plant-distribution, and for convenience we may recognize certain 

 climatic zones between the poles and the equator, although, of 

 course, these are by no means strictly limited by the parallels of 

 latitude. These zones may be denominated: Boreal, North 

 Temperate, Tropical, South Temperate and Austral. 



The distribution of land and water is very different in the north- 

 ern and southern hemispheres, and this difference is strongly 

 reflected in the climates. It is probable, however, that this 

 disparity has not always been so marked. At present it is partic- 

 ularly noticeable in the temperate zones. 



At the north, all of Europe, most of Asia, North Africa and the 

 greater part of North America lie between latitudes 25° and 60°, 

 and land extends without a break far beyond the Arctic Circle. 



In the southern hemisphere the only temperate area south of 

 50° is the extreme southern point of South America, while the other 

 temperate regions, New Zealand, Australia and South Africa all 

 lie north of 50°, and except New Zealand scarcely extend beyond 

 40°. To the south lies the unbroken Southern Ocean extending 

 to the shores of the ice-bound Antarctic continent. 



Due to latitude, and the proximity of the ocean, the south 

 temperate lands, for the most part, enjoy a very mild and equable 

 climate. Never, except at high altitudes are they subjected to the 

 severe winter cold that prevails at corresponding latitudes in most 

 of the north temperate zone, whose climate is, in the main, 

 decidedly continental in character. 



Melbourne, lat. 38° S. has a mean for the coldest month of 

 48.5°, for the warmest 67.5°; Philadelphia 39°57' N. 32° for the 

 coldest, 76° for the warmest; Wellington, New Zealand, 41° S., has 

 a range only of 14.9° between the warmest and coldest months, 

 while in Chicago, 41°53' N., it is 48°. 



The principal land-masses of the south temperate zone are 



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