17, 6 Trelease: Salt Requirements of Wheat Plants 549 
This form of leaf injury, which appeared in a few of the 
plants after about twelve days in the culture solutions and 
in more of them at the time of harvest, was characteristic of 
those cultures whose solutions had high ratios of magnesium 
sulphate to calcium nitrate. The two degrees of this injury, 
described by Shive as severe and as slight, were observed in 
this series and their distribution on the diagram is shown in 
fig. 2. In recording the occurrence of these two degrees of 
injury, when a spiral coiling was formed or the whole leaf was 
affected, the injury was considered severe ; when no spiral was 
formed and not the whole leaf was affected, the injury was 
considered slight. In fig. 2 the cultures marked with crosses 
showed severe injury, and those marked with circles slight 
injury. The number of leaves injured, in the entire culture 
of six plants, is shown by the numeral placed near the point 
of the diagram. 
Dry weights.—Since the roots and tops were weighed sepa- 
rately, two dry-weight data were obtained for each culture. The 
sum of these two weights, of course, gives the total dry weight 
of the plants in the cultures, but since this sum is generally 
controlled in its variation by the dry weight of tops, only the 
separate data for tops and for roots will be considered. 
These data are presented in Table 4, in which the first column 
gives the culture number; the second, the data for tops; and 
the third, the data for roots. The dry weights are expressed 
as relative numbers, in terms of the value for the highest actual 
dry weight considered as 100. The actual dry weight for this 
culture is given in parentheses below the value 100. The actual 
dry weights may be obtained by means of this value. 
High yields are indicated in the table by the letter H and 
low by the letter L. The method of defining high and low 
yields is as follows: The twenty-one cultures (one-fourth of 
the total number) giving highest yields are marked H, and the 
twenty-one giving lowest values are marked L. The remain- 
ing forty-two cultures (half of the total number) are considered 
as medium, excepting those which are numerically the same as 
the lowest of the “high” group which are marked H, and those 
which are the same as the highest of the “low” group which 
are marked L. The highest yield obtained in the series ig 
indicated by gothic type, and the lowest by italics. The average 
relative yields obtained with Shive’s and with Tottingham’s best 
solutions, employed as controls in this series, are given at the 
bottom of the table, for comparison. 
