No. 548] HARDINESS IN ALFALFA 465 



would have expected that they would have fared rela- 

 tively the same in the two winters. Deviations that 

 might appear could be charged to the differences of the 

 two winters, as we may suppose that alfalfa becomes ac- 

 climated in different ways to different types of cold. 



The relation of the killing of the plants in nursery A 

 and in series 201 is presented in the correlation table of 



x 



6 11 16 21 26 31 36 41 46 51 56 61 66 71 

 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 



Fig. 1. The means of nursery A are the average per 

 cents, of killing for the different strains, and the means 

 of the duplicate seeding, series 201, are the correspond- 

 ing per cents, for that nursery. In the table, the nursery 

 A means appear as subject, and the means of series 201 

 appear as relative. The table shows good correlation 

 amounting to + 0.62 ± 0.06, thus indicating that the two 

 series of alfalfa were affected relatively the same by the 

 two winters. This fact is perhaps more strikingly shown 

 when the two series of means are platted on coordinate 



