1915] | BAILEY & SHEPARD—SANIO’S LAWS 69 
EFFECT ed WIDTH OF RING UPON THE 
LENGTH OF TRACHEIDS 
TABLE VI 
Pinus Strobus, ECCENTRICITY DUE TO FASTER GROWTH ON 
E SIDE, AVERAGE 
TRACHEID LENGTHS— 
MILLIMETERS 
ANNUAL RING 
Narrow Wide 
PO or Gs Vopr ees 1.63 1.66 
: Ni hied ees Sok omen od 2.58 2.41 
Pleyel cbse vaietd Gata aa ene a 2253 
O vende uP Caaf ere: oi hes 2 2.24 2.20 
Discussion of measurements and conclusions 
The results of these measurements are obviously not in accord 
with SANIO’s first law, since no constant tracheid length was found 
in any of the specimens examined. Inasmuch as Santo found a 
constant in all cases within the soth ring, and in one case within 
the 2oth, and this study found none, even within the 23oth, it is 
evident that SANnro’s: first law cannot be applied to conifers, and 
some doubt is cast upon the accuracy of his observations upon 
Scotch pine. As is shown diagrammatically in the accompanying 
figure, the length of the tracheids increases rapidly for a period of 
years varying from 25 to 60. At the end of this period there is a 
marked falling off in the length of the tracheids, which lasts for a 
decade or more. Subsequently the tracheids again increase in 
length. In the case of the long-leaf pine, which unfortunately was 
the only very old material available, the tracheid length reaches 
a maximum at 160 years and decreases, with one marked period of 
recovery, during succeeding rings. The factor or factors which pro- 
duce the fairly regular cycles or series of crests and depressions which 
occur in the long-leaf pine curve are obscure and deserve to be 
Studied carefully by some one who has easy access to old coniferous 
trees. Douctass? and Huntrincton’s® interesting correlations 
* Dovetass, A. E., Weather cycles in the growth of big trees. Monthly Weather 
Review. June 1909. 
3 Huntincton, Extsworts, The climatic factor. Carnegie Inst. Washington, 
D.C. 1914. 
