64 



MADRONO 



[Vol. l, 



test of crucial experiment. I should have ascertained the direction 

 both of leaf -spiral and of fiber-twist in the same trees, stripping off 

 the bark to make sure of the latter. If in a sufficient number of cases 

 the two should be found to be either uniformly coincident or uni- 

 formly reversed, we should infer some causal relation, direct or in- 

 direct, between the two phenomena. On the other hand, if coinci- 

 dence and opposition were found to be not uniform, we should infer 

 either that these two phenomena are either wholly unrelated, or that 

 some other cause or causes interfere to modify or obscure whatever 

 relation might exist between them. My opportunity for making this 

 experiment was thus lost; but I trust that some one else may find 

 the problem sufficiently interesting to carry it through — and to re- 

 port the results. 



Meantime it may be well to examine a little into the nature of 

 the leaf-arrangement of this pine, and consider what possibilities it 

 affords for a causal relation between it and the twist of wood-fiber. 

 The accompanying diagram (Fig. 28) is an enlarged representation 



Fig. 28. Diagram of the Leaf -Arrangement of the Tamrac Pine 



of the surface of a short section of the terminal shoot of a young 

 tamrac pine in early spring, before it has attained its full length 

 and has consolidated its wood-fiber. The outer layer has been cut 

 open along a vertical line — which appears here at both the right- 

 hand and the left-hand margins of the figure — has been stripped 

 off and spread out flat. The numbered points are the positions of the 

 leaf-clusters. The primary, or fundamental, leaf-spiral is the line 

 which passes through all these points in order. It appears in the 

 diagram as a series of transverse lines rising at a low angle toward 

 the right. If the margins of the figure were rolled backward so as to 

 meet again as they do on the stem, these lines would form the con- 

 tinuous spiral just described. Along this spiral the leaf -stations are 



