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PLANT GEOGRAPHY 443 
shed their foliage, the leaves of many of them change from 
green to brilliant shades of red, yellow, and brown, and again 
the forest is strikingly beautiful. As the brightly colored leaves 
fall the forest enters the period of winter rest. 
Coniferous forests. Evergreen coniferous trees of the north 
temperate zone are adapted to withstand the desiccating effects of 

Fic. 497. Summer condition of a deciduous forest in the northeastern part 
of the United States 
winter by having xerophytic needlelike or scalelike leaves (Figs. 
475,479). The xerophytic structure of the leaves enables the 
trees to retain their foliage throughout the winter, the leaves of 
most species remaining on the trees for a number of years. The 
retention of the foliage throughout the year has the advantage 
that the leaves can carry on photosynthesis whenever conditions are 
favorable, while the same leaves can function for several seasons. 
Undergrowth is usually less dense in a well-developed, 
temperate-zone coniferous forest than in a deciduous one, This 
