6i MASS. EXPKRIMENT STATION BULLETIN 274 



Wliich are the Characteristic Leaves 



The leaves on any tree can be divided into two groups: (1) the "single" 

 leaves coming out on the current season's growth, and (2) the "rosette" leaves 

 coining out of buds formed the previous season, i. e., on wood of last year's 

 growth. The latter should be discarded, and study and attention centered on 

 the single leaves on the current season's growth. Leaves that have been in- 

 jured in any way, as by lice or other insects or by many scab spots or other 

 diseases, are of little value for identification purposes. Leaves on weak shoots 

 or in the interior of the tree should be avoided. Study the well-developed 

 •minjured leaves usunUij ftmnd along the middle of the season's growth. 

 Leaves on trees that are poorly nourished are often undersized and yellowish. 

 Such leaves are not typical and should be observed with caution. 



Inasmuch as leaves of the current season's growth are necessary, little prog- 

 ress can be made in leaf study until considerable growth has been made. 

 Leaves on trees or shoots making excessive growth are apt to be distorted and 

 are not typical. The most favorable period for observing the leaves is from 

 July 1 until October 1. To one familiar with leaf characters this period may 

 be extended somewhat. 



To the beginner in leaf study the leaves of all varieties will look alike. 

 rio.se and repeated observation will reveal differences that are peculiar to 

 different varieties. The purpose here is to discuss the various parts of the 

 leaf and how they dift'er in dift'erent varieties. 



The Petiole 



The petiole or stem of the leaf is sometimes characteristic of the variety, 

 though it is of minor importance. Wealthy has a rather long, slender petiole, 

 while that of Mcintosh is usually siiort and stout. The angle which the petiole 

 forms with the shoot on which it grows is often helpful in recognizing vari- 

 eties. In the Northern Spy the angle is sharp, that is, the leaf is said to be 

 upright; while in the Rhode Island Greening it is broad or spreading. This 

 character is correlated with the form of the top. The Northern Spy has an 

 upright head, while the Rhode Island Greening is distinctly spreading. This 

 character of the head or form of the tree is quite well known to fruit growers 

 and is further discussed eLsewhere; but few are aware that in an unknown 

 variety the form of the top can be foretold with considerable accuracy from 

 the leaf angles on a one-year whip. 



The Blade 



Size. — The leaf blade furnishes the most dejiendable characters for variety 

 identification. Consider first the size of the blade. This, of course, varies con- 

 iSiderably with the vigor of the tree. Trees in a sod orchard making little 

 growth will have much smaller leaves than will the same variety growing 

 under cultivation and making a vigorous growth. Leaves well exposed to tl>e 

 sun will often be smaller than those growing in shade. AVMth these reserva- 

 tions in mind, it may be said that the Jonathan (Fig. 29) has a small leaf, 

 while Rhode Island Greening (Fig. 18) has large leaves; Wealthy (Fig. 21) 

 is a little smaller than Baldwin (Fig. 4); and Mcintosh (Fig. 2) a little larg- 

 er than Wolf River (Fig. 3). 



