112 Principles of Plant Culture. 



vital activity is followed by one in which growth gradu- 

 ally declines until it almost or entirely ceases. In 

 woody plants, the cells become thickened and a part 

 of the rudimentary leaves change to bud-scales, which 

 inclose the growing point (127). In deciduous (de- 

 cid'-u-ous)* trees and shrubs, the chlorophyll and 

 starch, with mcst of the potash and phosphoric acid 

 contained in the leaves are withdrawn into the woody 

 parts (126), while the leaves themselves are detached and 

 fall. The root-hairs also die in many, if not all plants. 

 The leaves of many trees and shrubs assume striking 

 colors as they approach maturity. In perennial herbs, 

 the nutritive matters in the foliage and stem are with- 

 drawn to the underground parts. A period of almost 

 complete repose ensues, during which the plant, owing 

 to the dormant condition of its protoplasm, is able to 

 endure without harm extremes of temperatures or dry- 

 ness that would be fatal in its active state. 



Growth ceases in many trees and shrubs earlier 

 than is often supposed. Most orchard and forest trees 

 of mature age grow little, if any, after midsummer in 

 the temperate zones. Cultivation, mulching, manuring 

 and wet weather tend to prolong the growth period 

 (199). 



171. The Rest Period is Not Peculiar to the Tem- 

 perate Zones, but occurs in the tropics as well. It can 

 be ascribed in part to the change of seasons, as a few 

 familiar examples will indicate. Tubers of the earlier 

 varieties of the potato, that ripen in northern countries 



* Deciduous trees and shrubs are those of which the leaves 

 perish at the beginning of the rest period. 



