384 HOW CROPS GROW. 



other, and the whole combination is made to assume the 

 character of a fully-developed stem, -bearing its leaves at 

 regular intervals ; with these important differences, that 

 the portions of stem nearest the root extend more rap- 

 idly than those above them, and the stem has within it 

 the material and the mechanism for the continual for- 

 mation of new buds, which unfold in successive order. 



In Fig. 45, which represents the two terminal buds of 

 a lilac twig, is shown not only the external appearance 

 of the buds, which are covered with leaf-like scales, 

 imbricated like shingles on a roof ; but, in the section, 

 are seen the edges of the undeveloped leaves attached to 

 the conical axis. All the leaves and the whole stem of 

 a twig of one summer's growth thus exist in the bud, in 

 plan and in miniature. Subsequent growth is but the 

 development of the plan. 



In the flower-bud the same structure is manifest, save 

 that the rudimentary flowers and fruit are enclosed 

 within the leaves, and may often be seen plainly on cut- 

 ting the bud open. 



Nodes; Internodes. Nodes are those knots or parts 

 of the stem where the leaves are attached. The portions 

 of the stem between the nodes are termed internodes. 

 It is from the nodes that roots most freely develop when 

 stems (layers or cuttings) are surrounded by moist air or 

 soil. 



Culms. The grasses and the common cereal grains 

 have single, unbranched stems, termed culms in botani- 

 cal language. The leaves of these plants clasp the stem 

 entirely at their base, and rest upon a well-defined, thick- 

 ened node. 



Branching Stems Other agricultural plants besides 

 those just mentioned, and all the trees of temperate cli- 

 mates, have branching stems. As the principal or main 

 stem elongates, so that the leaves arranged upon it sepa- 

 rate from each other, we find one or more buds at the 



