Buds and Stems. 



6 7 



In other plants, such as the horse-chestnut, hickory, and 

 cottonwood, the elongation of the stem ceases before the 

 close of the growing season. In such cases a few of the 

 last-formed internodes fail to elongate, while the leaves of 

 some of the lower nodes subtending the short internodes 

 grow up in the form of scales, completely enwrapping all 

 of the parts above them, and protecting them against 

 mechanical injury and the 

 vicissitudes of weather. 

 Such buds are quite certain 

 to survive the winter, and, 

 if stronger than the lateral 

 buds, to continue the growth 

 of the shoot the following 

 spring, so that the main 

 shoot of such plants is apt 

 to retain its identity in the 

 form of a central shaft ex- 

 tending through the crown 

 (see Fig. 27). Buds which 

 ripen and prepare for winter 

 are termed winter buds ; 

 while the buds which do 

 not ripen, and die or re- 

 main weak in consequence, may be called summer buds. 

 49. Protection afforded Winter Buds. The study of the 

 winter buds of the horse-chestnut and cottonwood has 

 shown that the leaves formed at the uppermost nodes are 

 ordinary foliage leaves in an embryonic state, and conse- 

 quently in need of protection. The amount and character 

 of protection afforded to the tender parts of winter buds is 

 quite different for different plants. As has already been 

 observed by the student, the outer scales of the buds of 



FIG. 27. 

 Oak with excurrent trunk. 



