BUDS AND BRANCHES 



119 



the short branches are shed as well as the needle-leaves, 

 and the scars left on the axis are not leaf-scars, but the 

 scars of dwarf shoots. 



Vernation or pr defoliation. In the above examples we 

 have seen how neatly the leaves 

 are packed in the bud with the 

 least loss of space. The manner 

 in which leaves are thus folded 

 and arranged is known as ver- 

 nation or praefoliation, and 

 their relationship may be seen 

 by the examination of a trans- 

 verse section, or more easily by 

 a study of buds as they open in 

 the spring. Determine the ar- 

 rangement, manner of unfolding, 



and direction of greatest growth 



as the blades expand, in the 



following plants : the Dock and 



Rhododendron, where the leaves 



are back-rolled (revolnte) ; the 



Violet, Elder, Apple, Pear, and 



Poplar, where they are up-rolled 



(involute) ; the Plum and Black- 

 thorn, where they are rolled from 



one side to the other {convolute), 



and in the Ferns, where the 



blade is rolled from apex to base 



(circinate) . When revolute leaves 



expand, growth is greater on 



the under surface ; in involute, 



convolute, and circinate leaves 



growth during expansion is greater on the upper surface. 



Monopodialand sympodial branching. Trace the develop- 

 ment of shoots from the opening buds to the formation of 



s.s.2. 



Fig. 77. Winter Shoot 

 of Elm. f.b, flower-bud ; 

 Lb, leaf-bud ; l.s, leaf -scar ; 

 s.s.i to s.s.3, scale-scars of 

 three successive years ; t.i to 

 t.4, dead terminal buds of 

 four successive years. 



