CLONAL ROOTSTOCKS FOR THE APPLE 19 



Lenticels 



The lenticels or light colored dots on the bark are very distinctive. Thej' 

 vary in number, size, shape, and color. Some are flush, that is, even with the 

 surface of the bark. Others are more or less distinctly raised and can be felt 

 with the thumb or finger. This character also can be seen with a small magni- 

 fying glass. Those that appear in large numbers, are of large size, and are light 

 colored are the more conspicuous. 



Leaf Blade 



Some stocks have larger leaves than others though there is great variation on 

 a single plant. The observer should consider the normal well-developed leaves 

 located usually about in the middle of the shoot. They usually vary from oval 

 to ovate, but some stocks have leaves that are nearly round. Some have a dis- 

 tinct or rather long tip, while others have a very short tip or none at all. Most 

 leaves are more or less folded upward; sometimes the folding is near the edge, 

 while in others it begins near the midrib. Some stocks have leaves that are a 

 little folded downward. The leaf edge may or may not be waved, either finely 

 or coarsely. Rugoseness refers to the rough uneven surface of the leaf, while a 

 bullate leaf shows the net veining of the leaf quite distinctly. Glossiness refers 

 to the light reflection from the leaf surface. Young leaves near the growing tip 

 are more glossy than the other leaves below. One must compare leaves that are 

 of the same age. It is necessary to have a good light to do this. Differences 

 are not always easily seen, but when one learns to observe carefully in a good light, 

 it is of great help in identifying certain stocks. 



Leaf Base and Tip 



There are differences in the shape of the base of the leaf blade that are of 

 value in identifying rootstocks. The base is generally rounded but some are 

 broad while others have a tendency to narrowness. Some stocks show a tendency 

 towards a cordate or heart-shaped base. Usually the two sides meet the petiole 

 exactly opposite each other, but in some stocks there is a tendency for one side 

 to be lower than the other and these are described as uneven. 



Serrations 



The serrations along the leaf edge are very characteristic of the different stocks; 

 they vary in size, sharpness, and depth. On some leaves there is little space 

 between the serrations; while on others the serrations are well spaced and are 

 said to be distinct. Some rootstock leaves have serrations all very much alike; 

 others vary in size and depth; they are said to be regular or irregular, as the case 

 may be. 



Petiole 



The petioles or leaf stems vary in the angle which they form with the stem, 

 in length, and in thickness, and the differences though small are quite constant. 

 There seems to be little value for identification purposes in the furrow that is 

 always seen on the upper surface of the petiole. 



Stipules 



The stipules are two small leaf-like structures at the base of the petiole. They 

 vary somewhat in size and in some stocks there is a tendency for the stipules to 

 grow much larger than normal so that they resemble small leaves. The stipules 

 often drop off during the summer. Their persistency varies with conditions of 

 grow t h . 



