STEMS. 



141 



179. Tliepunctum vegetationis (growing point) of a stem 

 is generally a conical point ; upon its curved surface a little 

 below its apex the rudiments of leaves appear as slight swell- 

 ings or papillae ; as the growing point elongates, and the 

 rudimentary leaves grow, new ones appear above the pre- 

 viously formed ones. By the more rapid growth of the 

 leaves than the newer part of the stem, the latter comes to 

 be covered with many closely approximated young leaves. 

 This is the usual condition of the ends of growing stems in 

 summer, hence such an aggre- 

 gation of rudimentary leaves 

 may be termed a summer 

 bud. While in the apex of 

 the bud the leaves grow more 

 rapidly than the stem, in its 

 base the growth of the stem 

 is much the most rapid. This 

 later stem-growth is an inter- 

 calary one, and it results in 

 separating the previously ap- 

 proximated leaves a consid- 

 erable distance from one 

 another, forming the inter- 

 nodes of the stem. 



180. Winter buds have 

 essentially the same struc- 

 ture, and the same mode of 

 formation. In these, how- 

 ever, most of the phyllome 

 rudiments develop into more 

 or less hardened scales, which 

 grow rapidly and overtop the punctum vegetationis. The 

 basal growth of the bud ceases, and soon its apical growth 

 also, and thus the scaly phyllomes are left in close approxi- 

 mation (Fig. 121). Such a bud is but a state of the ter- 

 minal portion of the leaf-bearing stem, and not a new for- 

 mation or member ; it cannot even be called an organ. 



181, Upon the return of warm weather in the spring 



Fig. 121. Extremity of a branch of the 

 Horse-chestnut (JEsculvii hippocastanitm); 

 a large terminal bud with two smaller lat- 

 eral buds ; a, a, a, scars of fallen leaves. 

 Natural size. After Diichartre. 



wachse," p. 432, and Eichler's " Bliithendiagramme," page 33 et seq. 

 In each there are many references given to the literature of the subject. 



