76 MASS. EXPERIMENT STATION BULLETIN 159. 



stated in relation to the age of the tree. The size of the tree is determined 

 by the rate of growth in the past, while the vigor measures its current rate 

 of growth as indicated by the length and size of the shoots and the color, 

 size and abundance of the foUage. In vigor the tree may be weak, moderate, 

 strong or venj strong. Next comes the form of the tree which is often char- 

 acteristic and important in trees that are approaching or have reached 

 maturity. Most varieties begin to take on their characteristic form by 

 the time they are four to six years old. The form of the head may be flat, 

 round, oval, upright, spreading or drooping. The density of the head is 

 determined by the thickness of its branches and by the abundance of their 

 foliage. It may be dense, medium or open. 



Shoots. — The shoots comprise the last or current season's growth of the 

 more vigorous branches. In very young trees they indicate in some meas- 

 ure the adult form of the tree. Their length should be estimated on the 

 basis of a full season's growth. They may be short, medium or long, and 

 if the average length in centimeters or inches can be given, so much the 

 better. In size they may be stout, medium or slender, and if the diameter 

 preferably in millimeters, 2 inches or less above the last annual ring, is 

 given, it adds to definiteness. The direction of the shoots is of special sig- 

 nificance in very young trees. They may be upright, diverging, spreading, 

 drooping, ascending or irregular. The direction may be quite satisfactorily 

 determined by means of a simple protractor. It should be taken on a main 

 branch that is perpendicular. Shoots that are diverging form an angle of 

 about 45°, while ascending shoots are like upright ones, except that they 

 are more distinctly curved near the base. Under straightness-we record 

 whether the shoots are straight or zigzag. In the latter case the successive 

 internodes do not lie in the same direction, but alternate back and forth. 

 Under curvature the shoots may be more or less curved or not curved. The 

 length of the internodes varies somewhat in different varieties, and they 

 may be short, medium or long. 



Bark. — The color of the bark varies with the season. In the summer 

 it is some shade of greenish olive or yellowish olive, and the color darkens 

 with the falling of the leaves to a greenish, yellowish or reddish brown. 

 The full description of a variety ought to include both the summer color 

 and the winter color. The summer color should be taken on wood of the 

 previous season's growth, as that of the current season's growth is apt to 

 be variable. The surface may be shining or dull, and in thickness the 

 bark may be thick, medium or thin. The amount of pubescence on the 

 young 'shoots — much, medium or little — should be mentioned, and 

 whether it is fine or coarse. 



The lenticels are often characteristic of the variety, and they seem to be 

 quite dependable in identification.' The number — few, medium or many 

 — is most valuable, and should be carefully noted. Their size — small, 

 medium or large — should find mention, also their form, which is com- 

 monly roundish but may be oval or flattened. Their color is commonly 

 whitish, gray or brown. The position of the lenticels is of especial impor- 



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