384 ' BOTANICAL GAZETTE [may 



in this paper, all of the tangents used in measuring intake velocities 

 would have fallen on that part of the curve between the point of 

 origin and the first reading, all of which is constructed from imagina- 

 tion, as an "ideal curve." In the case of barley it is not so serious, 

 but it is only in the 3 . 8° curve that all of the tangents fall beyond 

 the first observation. ' In their 21.1 curve the first observation 

 showed over 9 per cent of intake, from which it is seen that the 

 5 and 7.5 per cent tangents were measured on a " guess curve" 

 between the origin and the first observation, and the 34 . 6° curve 

 is still less favorable; for in it the first observation shows 

 nearly 17 per cent of intake, so that 4 out of 6 tangents used were 

 measured on a curve constructed entirely without data. This 

 matter is vital to the whole theory they propose, for they had but 

 three points in plotting logarithms of velocities against tempera- 

 tures, and if one of the points is insecure no conclusions can be 

 drawn. The other two points are bound to be in a straight line. 

 In four cases out of six, the third point is not established by data, 

 and in two of the plotted logarithm-temperature curves, both the 

 second and the third points are derived from tangents whose 

 determination is insecure. The evidence offered, therefore, that 

 the velocity of intake is an exponential function of the temperature 

 is not very convincing. In this work I have used short time inter- 

 vals to understand better the curve whose tangents were to be 

 measured. Our short intervals have the disadvantage that water 

 movement goes on in the seed during weighing which occurs fre- 

 quently. There is no intake during weighing, of course, but dis- 

 tribution of water already taken in continues. I have felt that 

 the advantages of the close intervals between weighings exceed 

 by far any disadvantage that might exist. 



In the case of Xanthium, with a semipermeable coat, and in 

 split peas without the coat, I have found that the plotting of 

 logarithms of velocity against temperatures does not yield straight 

 lines. The nearest approach to straight lines is seen in the upper 

 half of fig. 3, but even here there is a slight divergence, always in 

 the same direction. A somewhat greater divergence from straight 

 lines is seen in the lower half of fig. 3, and a very marked divergence 

 is seen in fig. 4, in the case of split peas. From the data I conclude 



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