HARRIS: INTERRELATIONSHIP IN PHASEOLUS 169 
seed flat were potted side by side in a three inch pot and allowed to 
grow to the proper stage of maturity under conditions as favorable 
as we were able to give them. 
Before the samples were taken, the plants were carefully inspected 
and all pairs, one member of which had died, had been injured or 
which showed in its subsequent development any abnormality in addi- 
tion to these specified were discarded. Note that there was no direct 
selection for the characters of the abnormal plantlets in this process, 
since both abnormal and control were discarded if either was unsuited 
for the purposes of the experiment. 
There probably was a fairly stringent imdzrect selection, since the 
death rate and the mutilation rate of the variant individuals was 
probably greater than that of the normals. Thus more pairs were 
probably discarded because of an injury to or the death of the ab- 
normal member of the pair than because of the death or injury of a 
normal member. 
The probability that the materials were somewhat selected before 
the physiological measurements discussed in this paper were carried 
out renders the findings of greater significance than they would 
otherwise be. 
After the pairs of seedlings had grown until the first compound 
leaf had attained its full size, and the second compound leaf was 
developing, but before the primordial leaves had materially deteri- 
orated, samples of leaves were taken by nipping off the laminae only, 
or the laminae and the single petiolule of the terminal leaflet in the 
case of the compound leaf. These samples of tissues, each from 
100 plants, were enclosed in flasks, weighed, and dried to constant 
weight in a bath surrounded by boiling water. 
Thus the technique employed was exceedingly simple. Because 
of the size of the samples dealt with, the relative infrequency of the 
abnormalities, and the large number which had to be discarded, the 
routine has been excessively laborious. For example, the weighings 
of the 23 samples and checks discussed in the present paper involve 
13,800 leaves gathered from 4,600 plants which were secured by 
germinating and classifying nearly half a million seedlings. 
The structural variation in the bean seedling which is probably the 
simplest, and the most frequent, is a slight vertical separation of the 
cotyledons which are normally sensibly opposite in insertion. The 
amount of the separation is difficult to express quantitatively, since 
it is in some degree dependent upon the length of the axis. In our 
studies of seedling variation in Phaseolus, three grades of separation 
of the cotyledons have been recognized. The line of demarcation 
between these grades is a quite arbitrary one. This is also true of 
