Pollination 287 



umn indicates the pomological group to which each 

 variety belongs. This is a matter of some importance 

 in selecting varieties for cross-pollination, as will be 

 explained later. The third column shows the num- 

 ber of observations which have been made of the 

 blossoming time of the variety. The heavy horizontal 

 lines represent the periods during which the several 

 varieties are generally in blossom. One can tell, 

 therefore, by comparing two varieties in the chart, 

 whether they blossom nearly enough together to make 

 them safe mutual pollenizers. 



This chart is made up largely from notes taken 

 in the orchards of Mr. J. W. Kerr, at Denton, Mary- 

 land, which is about the latitude of Washington. This 

 is a convenient latitude, being about midway north 

 and south in the plum-growing area of the continent. 

 Southward from Washington the blossoming season 

 is earlier, and it is also longer. The further south we 

 go the longer the season is; and the further north we 

 go, the shorter it is. We thus find greater difficulty 

 in arranging varieties so as to have them bloom to- 

 gether in the southern states than we do in the north- 

 ern states, or in Canada. 



These facts should be borne in mind in making 

 use of the blossoming chart. It also raises the ques- 

 tion as to whether or not a chart made for one locality 

 will be of any use in another latitude. The author has 

 made several careful examinations of this question, 

 from which he has concluded that a general chart of 

 this sort has its limitations, and that a chart made for 

 a particular locality, from blossoming records taken 

 at the same place, is more reliable. In the absence of 

 local notes, however, it seems that a general state- 

 ment like the one here given is so nearly correct that 

 it can be used without much fear of mistake. 

 With these explanations the chart is submitted. 



