ii8 



General Botany 



The opening of 

 buds. When the 

 warm weather of 

 springtime comes, the 

 innermost bud scales 

 begin to grow and ex- 

 pand. Sometimes the 

 outer scales are pushed 

 off ; sometimes they 

 elongate and grow Hke 

 the inner ones. But 

 the scales quickly 

 reach their full 

 growth, and soon they 

 are cut off by the for- 

 mation of an abscis- 

 sion layer at the base 

 of each. In the buds 

 of a few plants all the 

 scales are dead and 

 are pushed off by the 

 growth of the stem 

 and leaves inside. 

 The expansion of bud 

 scales and leaves 

 takes place partly 

 through cell multipli- 

 cation and partly through the enlargement of cells already 

 formed the preceding year. Within the bud the minute leaf 

 cells absorb water and develop large vacuoles. The expansion 

 of these cells results in the enlargement and spreading of the 

 leaves. Material for the study of the different habits of bud 

 expansion may be secured in winter by bringing branches of 

 different kinds of trees into a warm room and placing them in 

 water until the leaves expand. 



Fig. 66. Date palms in fruit, on an oasis in the Algerian 

 desert. The strong terminal bud, and the failure of the 

 lateral buds to develop, leads to an unbranched stem. 

 An unbranched stem is more common among monocots 

 than among dicots. {From photo U. S. Dept. of Agricid- 

 ture.) 



