188 



BAILEY AND TUPPER. 



the formation of shorter tracheary elements, A Fig. 4, Graphs 15 and 

 15v. Similarly, the size of the tracheary cells tends to be less in nodes, 

 junctions of stems and roots or branches and other regions where 

 growth adjustments are taking place. Table V. 



^ 3 



AGE-ANNUAL |)INGS 



Figure 3. Graphs iUustrating effects of environmental factors on lengths 



of tracheids. 12. Pinus Sirobus, vigorous, rapidly grown siiocimcn; r2a. 



Same, i)lant sui)])rossed during first 60 years; 5a. Piinis pnndcro.'<ii, effects of 



injury at A; 5b. Satiie, stunted si)ccimen, 12 feet high at 100 years; 8. Pinus 



' albicaulis, alpine plant, one foot high at 45 years. 



Therefore, longer tracheary elements tend to occur in tlu> "clear 

 lengths" of the stems of tall, vigorous, rapidly growiug forest trees, 



