6 Tlili I'LAXr WORLD. 



buds for the following year arc formed at this time and the 

 growth is finished for the season m May or June, the end of n. ■ 

 twig having ]^roduced a terminal bud. Such growth is often 

 called definite or determinate. The growth in length is not al- 

 ways so definite and may extend through the season until stopped 

 by the advent of cold weather. As examples of this may be 

 mentioned some of the willows and the genus Riibiis. Xo defi- 

 nite terminal bud is then formed. Other plants have adapted 

 themselves by an intermediate process which may be termed the 

 casting of deciduous tips. The smooth sumac is a good illustra- 

 tion of this. The growth of the t^vig is indefinite, but in the fall 

 the terminal portion of the twig (some four or five inches), is 

 cast off b\- the formation of a corky layer in the same wav as 

 leaves are cast. The uppermost lateral bud is strong and con- 

 tinues the growth of the twig, while tlie dead portion falls off 

 during the winter, leaving a scar which represents the end of the 

 twig. In other genera this habit of casting has become so fixed 

 that it takes place early in the season, about the same time that 

 the terminal buds are formed in such plants as the hickory. If 

 these twigs are examined in early summer the dwarfed terminal 

 portion, sometimes an inch or so long, can be seen, but it soon 

 falls away, leaving a scar. Such casting of the tips is common 

 in the 2-ranked twigs. The elms, mulberry, and basswood will 

 all show a terminal scar, usually pushed aside by the vigorous 

 uppermost lateral bud which continues the growth of the stem. 

 The axes of such plants are. of course, always s\mpodial. 



The lateral Ijuds are normally single in the axils of the leaves 

 but ma)- be superposed, that is, two or more, one above the other, 

 in which case the uppermost in the largest. Superposed buds 

 are shown in some of the hickories (c. f^. Hicoria mini ma 

 (Marsh.) liritt. ) and several Leguminosae (the Kentucky coffee 

 tree Gyiiiiiocladus, the honey-locust Glcdifscliia, etc ). In Glc- 

 ditschia, a longitudinal section through the leaf-scar and twigs 

 reveals a row of six or eight buds, the lower successively smaller 

 and hidden by the scar, while the ui)])erniost is usuall}- trans- 

 formed into a more or less branched tliorn. 



In some si)ecies the fiower buds are conspicuous during winter 



