BUDS AND STIPULES 



at the summit of each twig and in the axil of each 

 leaf. 



When the year is divided into favourable and un- 

 favourable seasons, marked either by alternations of 

 temperature or by drought and rain, there is often a 

 marked difference between 'growing' and 'resting' 

 buds. Moreover, among our own species there is often 

 a considerable difference be- 

 tween terminal and axillary 

 buds, as, for instance, in the 

 Black Poplar (Populus nigra). 



The following figure (fig. 1 ), 

 representing a young shoot of 

 a Tulip Tree, is an illustration 

 of the necessity for such protec- 

 tion. It will be seen that the 

 outer (lower) leaf, which had 

 only a single covering, has been 

 killed by frost, while the suc- 

 ceeding one, which had two 

 wraps, has escaped. 



It is remarkable that some 

 nearly allied genera, and even in certain cases species 

 of the same genus, often differ in the method of the 

 protection of the bud. This is the case, for instance, 

 in the Willows and Poplars, the function being per- 

 formed in the Poplars by stipules, in the Willows 

 (though thsy possess stipules) by leaves. 



Fig. 1. Young Shoot of 

 Tulip Tree (Lirioden- 

 drcni), 1 nat. size. 



