Geography and Climatology 309 



noted that we have greater complications than with 

 any other class of fruits, from the fact that the plums 

 belong to so many different species, and from the ad- 

 ditional fact that these species have been badly mixed 

 by natural and artificial hybridization. In a general 

 way, however, we understand the capabilities and re- 

 quirements of the several groups of varieties; and these 

 requirements may be more definitely stated according 

 as a given group is more homogeneous and invariable. 

 The Americana group is the most hardy and the 

 Chicasaws are generally tender in the northern states. 

 The general range of the several groups has been indi- 

 cated in the separate chapters where those groups are 

 discussed, and need be renewed here only in a gen- 

 eral way. 



Two years ago the writer made a special investi- 

 gation of the hardiness of plums, the results of which 

 were published in the eleventh report of the Vermont 

 Experiment station. Some of the notes given there 

 may be conveniently reproduced here. 



Largely through the aid of expert correspondents, 

 statistics were gathered concerning the hardiness of 

 representative varieties in the leading groups. These 

 are summarized in the following table. 



Notes of hardiness can be best generalized on a 

 map, however. If we take up the principal groups in 

 order, we shall find it possible to draw certain lines of 

 northern limit which indicate in a rongh way the hor- 

 ticultural range of the varieties. 



Domcstica group. — Taking Lombard as a repre- 

 sentative of this group and examining carefully the re- 

 ports of correspondents, the results published by the 

 experiment stations and horticultural societies, and 

 taking practical experience into account, we may safe- 

 ly trace the northern limit of Lombard by the upper 

 line in the accompanying map. 



