LEAF-GLANDS 



inner, helps materially to identify all species 

 of drupe-fruits, and is a means of recognizing 

 many varieties. Bark is usually lighter in color 

 in warm than in cold climates; in dry than 

 in wet regions. On young trees, the bark is 

 smoother and brighter than on old, as it is 

 also in healthy, vigorous specimens. 



Branches and branchlets. 



The branches and branchlets of both species 

 and varieties are very characteristic. The 

 length, thickness, rigidity, branching angle, and 

 direction are all very characteristic and change 

 but little with variations in soil and climate. 

 The branchlets may be short or slender; long- 

 jointed or short-jointed; straight or zigzagging ; 

 variously colored; those of some species or 

 varieties are pubescent at one stage or an- 

 other, while those of others are glabrous at 

 all stages of growth. It is of much importance 

 with the drupes whether they are armed or 

 unarmed with thorns or spurs, nearly all species 

 being armed. In particular, the character of 

 the spurs is important in identifying some of 

 the native plums. The length of the internodes 

 and the shape of the nodes are important char- 

 acters. Although exceedingly variable, the 

 presence and amount of pubescence, and the 

 size, color and number of lenticels on young 

 wood are important in distinguishing botanical 

 and horticultural groups. The color of the 

 wood is also of taxonomic importance. The 

 presence or absence of excrescences is always 

 to be noted, since some plums may be so 

 identified. 



Leaf- and fruit-buds. 



Both leaf-buds and fruit-buds are of much 

 value in separating species, and may often be 

 used in distinguishing varieties. Thus, fruit- 

 buds are borne in pairs with a leaf-bud separat- 

 ing the members of the pair on peach wood; 

 flower-buds are borne in triplets in Japanese 

 plums; and in other species may be borne 

 singly, in pairs, or in rosettes. Size, shape, 

 color, position, and angle must all be taken 

 into account. The outer and inner scales and 

 the margins of the scales vary greatly, and so 

 offer stable differences in different species. 

 Vernation, or the disposition of the leaf-blade 

 in the bud, is a fine mark of distinction in 

 separating cherries from other drupe-fruits; 

 and, while all cherries are supposed to be 

 conduplicate (folded on the midrib so that 

 the two halves are face to face), yet there are 

 important differences as to the manner of 

 conduplication in both species and varieties. 

 Leaves of plums are usually convolute (rolled 

 up in the bud), but in a few species they are 

 conduplicate, an indication of the close re- 

 lationship of cherries and plums. 



Leaves. 



After the fruits, leaves are the most useful 

 organs as determinants of both species and 

 varieties. Leaves vary but little and only 

 under easily recognized conditions; as, in 



young plants, on water-sprouts, and in ex- 

 tremes of soil, light, moisture, and temperature. 

 Only leaves found on normal wood should 

 be studied. Leaf-size is the most variable 

 character of leaves, yet it serves to distinguish 

 varieties in every species of drupe-fruits; size 

 should be designated by figures. Leaf-form is 

 the most stable leaf-character, hence especially 

 valuable in classification. The bases and apices 

 of leaves usually afford valuable distinguishing 

 marks of the drupe-fruits. The time of ap- 

 pearance and the time of dropping are impor- 

 tant in distinguishing any of the drupes. The 

 margins of leaves in all species in this group 

 of fruits are very characteristic, and often serve 

 to identify varieties as well. In studying mar- 

 gins, both serrations and glands are most con- 

 stant in the middle of the sides of leaves, those 

 at the base and apex often being crowded or 

 wanting. In the drupe-fruits the margins may 

 be serrate, crenate, toothed, doubly or singly 

 divided, glandular or glandless, never entire. 

 Margins of leaves of the drupe-fruits are some- 

 times more or less hairy. The color of leaves is 

 very constant in species and varieties, when 

 studied in individuals or taken in mass. Nearly 

 all species and many varieties are given a dis- 

 tinct aspect by their summer dress, which is 

 chiefly dependent on the color of the leaves, 

 that of both upper and lower surfaces being 

 constant. Pubescence, texture, thickness, and 

 the reticulation of leaves must be taken into 

 account in determining species, but are of 

 small value in naming varieties, although all 

 are variable in accordance with age of leaf, 

 and the soil and climate in which the plant 

 grows. The petiole may be used to good ad- 

 vantage in determining species and varieties. 

 Thus, in consequence of the great length and 

 slenderness of the petiole in sweet cherries, 

 the leaves droop, while because of the short, 

 stout leaves of sour cherries, the leaves are 

 usually erect. The color of the petiole of the 

 leaf in some stone-fruits is correlated with that 

 of the fruit. Pubescence must be noted. 

 Stipules offer little evidence of value in any 

 of the drupe-fruits except in the cherry, with 

 which fruit they have considerable value in 

 separating even closely related varieties. 

 Stipules appearing with the first leaves of the 

 cherry are small and drop before the fruit 

 ripens; stipules appearing with later leaves are 

 large, borne in pairs, and remain until fruiting 

 is past; the season of dropping depends much 

 on the variety. Stipules of cherries are usually 

 deeply toothed and bear glands of varying 

 color and shape which are characteristic. 

 Many of the distinguishing marks mentioned 

 under leaves apply to stipules. 



Leaf-glands. 



Much use is made of the glands on leaf- 

 stalks in classifying peaches. Their presence 

 or absence, size, color, position, shape, and 

 number must be noted, and whether stalked 

 or sessile. Two kinds may be found; globose, 

 those which are small globes; and reniform, 

 those which are kidney-shaped. In studying 



