IDENTIFICATION OF PLUM VARIETIES 



13 



more mature leaves. This pubescence is usually very fine and is often rather 

 difficult to observ-e except on a few varieties, as Early Laxton, where it is quite 

 prominent. Furthermore, the length and location of pubescence is variable. 

 For instance. Yellow Egg and Italian Prune have quite long hairs. Those of 

 Yellow Egg are on the surface of the blade tissue while those of Italian Prune are 

 fewer and confined to the midrib and principal veins. Occasionally the pubes- 

 cence is coarse and stiff — hirsute — and the upper leaf surface feels bristly or 

 gritty to the touch as in Beauty (Figure 9). 



The amount of light reflection from leaves is variable, depending not only on 

 variety but also on leaf age, time of observation during the growing season, 

 amount of dust on the leaf surface, and brightness of the day. Despite these 

 secondary influences, light reflection can still be a valuable distinctive character 

 (Figure 10). President and Glass are described as very glossy or shiny. A 

 number of varieties, as Golden Drop, are usually semi-glossy, and others, as Early 

 Laxton, are dull. With one variety. Elephant Heart, many leaves are waxy- 

 glossy. 



1. PRESIDENT— glossy ; 



Figure 10. Light Reflection. 

 2. GOLDEN DROP— semi-glossy; 



3. EARLY LAXTON— dull. 



Although leaf color ma\- be influenced considerably b\- environmental conditions, 

 particularly nutrition, this character is one of the first that is taken into con- 

 sideration when examining nursery trees. When its limitations are fully realized, 

 its value in identification work is great. The color of fully developed leaves on 

 vigorous shoots may be typically light green as in Early Laxton, medium green 

 as in Bavay, rather dark green as in Albion or dark green as in Glass. Also, 

 there is a good deal of yellow in the leaves of some varieties. Thus Burbank is 

 described as medium yellowish green and Italian Prune as dark yellowish green. 



Late fall coloration may be useful with the Japanese and some hybrid varieties. 

 For instance, while Santa Rosa remains green, and Elephant Heart foliage usually 

 turns slightly red, that of Red June becomes almost uniformly red. The follow- 

 ing tabulation gives the fall foliage coloration for the year 1943. 



