33^ 



Introduction to Botany. 



phenomenon of flowers and fruits borne on the old 

 branches and even on the trunks of trees, as shown in 

 Fig. 182. 



In the moist forests the buds of trees do not prepare for 

 their period of rest by the production of elaborate scales, 



such as are found in the winter 

 buds of trees of temperate re- 

 gions, and the resumption of 

 growth of resting buds does 

 not differ essentially from the 

 uninterrupted apical elongation 

 of shoots at the height of the 

 growing season (Fig. 183). 



214. Vegetation in Temperate 

 Regions. — The temperate re- 

 gions are characterized by much 

 greater extremes of temperature 

 than occur in the tropics, the 

 minimum for the winter months 

 running in some places far below 

 the freezing point, and the maxi- 

 mum in summer rising as high as 

 50° C. (122° Fahr.). Those por- 

 tions of the temperate zones 

 which lie next the tropics gradu- 

 ally blend with the latter in their 

 physical characteristics and veg- 

 etation. The amount of precipitation is much less in the 

 temperate zones than in the tropics, the greater part of 

 Central Asia and large parts of Europe and western North 

 America having an annual rainfall of 20 to 60 centimeters, 

 while the deserts of North America and the greater part 

 of the Sahara and of the great deserts of Asia, where the 



Fig. 183. 



A', young shoot, with apical bud, 

 of Tabernaemontana dichotama ; 

 L, young shoot of Clusia grandi- 

 Jlora{'>). After P. GROOM. 



