21 



larger here, often twice the normal diameter of that just above 

 or below ; its cells are smaller and thicker-walled and inclined 



r 



to be elongated and arranged in longitudinal rows, as if to 

 add rigidity to this portion of the twig during the early spring 

 growth, and give general stability at a point where elements 

 of weakness naturally obtain from the union of the wood of 

 two different years. Below the juncture the pith contains a 

 cone or thimble, the outer cells of which are usually tinged 

 with brown as if dead, and in shape and position it accords 

 with the exterior of the lignified pith which has been men- 

 tioned as beginning a short distance below the base of the 

 terminal bud. With certain chemical reagents and coloring 

 materials this thimble or cone of pith, surrounded by struc- 

 turally almost identical tissue, behaves the same as that at the 

 top of a w^ell-matured twig, and easily met with by cutting 

 down through the terminal bud lentrthwise with a razor or 



t> 



t> 



sharp knife. It is evident, therefore, that as the terminal bud 

 undergoes development in the spring, the soft thin-walled cells 

 at its base become lignified, and while they are finally appa- 

 rently the same in structure as the cells below them which 

 were lignified the autumn before, the line of separation is not 

 obliterated, but instead may be usually observed, without 

 the aid of a magnifier, by making a longitudinal section 

 through the juncture. 



The point that most interests us in this connection is the 

 important part which the juncture plays in the storage of 

 reserve material, and especially starch. Having become 

 adapted for this service while situated in the vicinity of the 

 terminal bud, the lignified pith cells continue for several years 

 in the same capacity, and probably at no time become entirely 

 free from these substances. Trees and all starch-bearing 

 shrubs exhibit this fact, but some much better than others. 

 For example, the pear is shown in figure 7 as a type of the 

 large class of trees. Figure 8 is of the honey locust, which is 

 without a well-formed terminal bud, and" the branch is each 

 year continued by a lateral bud. Twngs with opposite buds, 

 which, of course, from what has been seen of the relation 

 between buds and starch storage, have the amount of food- 

 reserve doubled at any one transverse plane of the node, are 



