CHAPTER VII 



BOTANY OF THE DRUPE-FRUITS 



A drupe is a fruit consisting of a fleshy or 

 leathery, valveless exocarp (the pulp of the 

 peach, plum, cherry and similar fruits) and a 

 hard, bony endocarp (the stone of the fruits 

 named) enclosing a single seed. The drupe- 

 fruits, sometimes called the stone-fruits, are 

 the almond, apricot, cherry, peach, and plum, 

 represented by many species. All belong to 

 the genus Prunus, a member of Rosaceae, to 

 which family, as we have seen, belong also 

 pomes, brambles, and strawberries. To be 

 able to distinguish the species and their many 

 horticultural varieties, the student must know 

 the gross structure and the habits of growth 

 of the great botanical group constituting the 

 drupe-fruits. 



Size and habit of tree. 



Species of the stone-fruits have very charac- 

 teristic trees, a glance usually enabling one to 

 tell one species from another. So, also, many 

 of the varieties of different species are readily 

 told in the orchard by the size and habit of the 

 plant. Size, it must be remembered, responds 

 to environment food, moisture, light, isola- 

 tion, pests, and the like but, making proper 

 allowance, size of tree, or of its parts, is a 

 reliable character by which to determine either 

 species or varieties of the drupe-fruits. There 

 are no true dwarfs in any of the cultivated 

 drupes in America. As with the pomes, the 

 terms large, small, and medium are used to 

 designate size. Habit of growth is nearly as 

 important as size, and as it is affected but little 

 by environment, becomes a most important 

 means of distinguishing groups. For example, 

 the tree of a species or variety may be up- 

 right, spreading, drooping, or round-topped; 

 the top may be open or dense; the branches 

 may form a vase or pyramid; the trunk may 

 be short and stout or long and slender, straight 

 or crooked, smooth or gnarled; the trees may 

 grow rapidly or slowly; and may be long-lived 

 or short-lived. These habits of growth not 

 only help to distinguish varieties, but very 

 largely determine whether the plant is suffi- 

 ciently manageable to make a good orchard 

 plant. 



Hardiness. 



The degree of hardiness is most important 

 in classifying drupe-fruits. In the case of the 

 sweet cherry, peach, and plum, varieties tol- 

 erate widely varying degrees of cold; in the 

 case of the sour cherry, great differences in 

 heat. In one of the classificatory schemes for 



the peach, that of Onderdonk and Price, hardi- 

 ness is the chief determinant of groups. The 

 range in hardiness of varieties falls within that 

 of the wild species, as it is seemingly impossible 

 to develop a variety hardier than the species 

 from which it comes. Varieties of drupe-fruits 

 are designated as hardy, half-hardy, and tender. 

 In North America, artificial protection is sel- 

 dom given to tender drupe-fruits, as is often 

 done in Europe, although peaches, apricots, 

 and nectarines are occasionally grown under 

 glass. 



Fruit-bearing. 



Productiveness, age of bearing, regularity in 

 bearing, and certainty of bearing all count in 

 classifying any of the drupe-fruits, though of 

 much less importance for this purpose than 

 in pome-fruits, since the drupe-fruits usually 

 bear early and are productive and regular in 

 bearing; otherwise they are not chosen for 

 cultivation. The care given trees greatly in- 

 fluences all of these characters, and in using 

 them allowance must be made for culture, as 

 also for soil, climate, light, pests, and other 

 environmental conditions. Length of life must 

 be noted in describing species and varieties, as 

 a characteristic difference. 



Resistance to disease. 



Susceptibility and immunity to disease and 

 insects are valuable taxonomic characters. 

 There are great differences among varieties of 

 peaches in resistance to the yellows, little- 

 peach, and leaf-curl; in plums, to brown-rot 

 and black-knot; in cherries, to leaf-spot and 

 gummosis; and in all drupe fruits to San Jose 

 scale, borers, and plant-lice. Resistance to 

 pests, obviously, is of great economic impor- 

 tance, and the reactions of varieties to pests, 

 so far as they can be determined, should al- 

 ways be stated in a description of a fruit, 

 whether or not they may be used in classifica- 

 tion. Both insects and fungi may vary in 

 destructiveness from year to year and, no 

 doubt, the host-plant may acquire new rela- 

 tionships to either insect or fungous pests. 



Bark. 



The thickness, smoothness, and manner of 

 exfoliation of the bark have great value in 

 determining species of drupe-fruits, but are of 

 little use in distinguishing varieties. Any one 

 of the ten or twelve species of cultivated plums 

 can be recognized by the characters of the 

 bark. Color of bark, both the outer and the 



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