6 THE PLUMS OF NEW YORK. 



dicated in the preceding paragraph. With this end in view the first task 

 is to name and discuss briefly the characters of plums whereby species 

 and varieties are distinguished, with a statement, so far as present knowl- 

 edge permits, of the variability of the different characters. It is absolutely 

 essential that the plum-grower have knowledge, especially if he aspires 

 to improve the fruit by breeding, of the characters of the plants with which 

 he is to work. These are in the main as follows: 



All species and some horticultural varieties have more or less charac- 

 teristic trees. Making due allowance for environment — food, moisture 

 and light — many plum groups can be readily distinguished by the general 

 aspect of the plant. Of the gross characters of trees, size is usually most 

 characteristic. A species, for example, is either shrubby or tree-like. 

 Yet under varying environment, size of plant and of the parts of the plant, 

 are probably the first to change. Habit of growth is nearly as important 

 as size and varies but little under changing conditions. A species or 

 variety may be upright, spreading, drooping or round-topped in growth; 

 head open or dense; the tree rapid or slow-growing. Hardiness is a very 

 important diagnostic character, plums being either hardy, half-hardy or 

 tender. Both species and varieties respond in high degree to the test 

 of hardiness, the range for varieties, of course, falling within that of the 

 species. Productiveness, regularity of bearing, susceptibility to diseases 

 and insects, and longevity of tree are all characters having value for species 

 and varieties and with the exception of the first named, are little subject 

 to variation. 



The thickness, smoothness, color and manner of exfoliation of the 

 outer bark and the color of the inner bark have considerable value in deter- 

 mining species but are little used in determining horticultural groups. 

 It is well recognized that all plums have lighter colored bark in the South 

 than in the North. The branches are very characteristic in several species. 

 The length, thickness and rigidity of the branch and the length of its 

 intemodes should be considered, while the direction of the branch, whether 

 straight or zigzag, are very valuable determining characters and relatively 

 stable ones, seeming to change for most part only through long ranges 

 of climatic conditions. So, too, the arming of a branch with spines or 

 spurs and the structure of such organs are important. The color, smooth- 

 ness, amount of pubescence, direction, length, thickness and the appear- 

 ance of the lenticels, the presence of excrescences on the branchlets of 

 the first and second }'ear's growth and the branching angle, are all worthy 



