142 



BOTANY. 



the basal growth of the bud is resumed, and shortly after- 

 ward, or simultaneously, the apical growth also. The thick 

 scales separate by the slight elongation of the stem, and being 

 of no further use to the plant they soon fall ofE. The inter- 

 calary growth of the scale-bearing portion of the stem is gen- 

 erally much less than of that which bears leaves, hence the 

 first internodes which appear in the spring of the year are 

 quite short. The punctum vegetationis of such a winter 

 bud, after resuming its activity, goes on developing leaves as 

 lateral members exactly as if there had been no interruption 

 in its activity. Upon the approach of autumn again the 



Fig. 128. — Longitudinal section of the apex of the stem of a mosa {Fontinalis anU- 

 pyrelica). v, apical cell ; a, outer part of one of the segments cut off from apical 

 «eU ; e, apical cell of a lateral leaf-bearing shoot arising below a leaf; c, first cell of 

 a leaf ; ft, 6, cells forming cortex —After Leitgeb. 



same process of bud-formation takes place by the decrease in 

 the rapidity of extension, and its final cessation ; this is fol- 

 lowed again by the resumption of growth upon the advent of 

 spring. Thus the stem exhibits a periodicity in its growth, 

 and one of its phases is the so-called winter bud. 



182. — Branches of stems (lateral stems) normally originate 

 in the punctum vegetationis as lateral outgrowths (Pig. 

 133, z) ; each develops first into a conical mass, which then 

 becomes the punctum vegetationis of a new stem, and upon 

 it lateral members arise, as in the case of the principal stem. 

 The new stem may elongate at once into a leafy shoot, as 



