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through all the results, and that is chat the regulatory changes 
following the operation are in the direction one would expect 
them to take in forming a new symmetrical system based on 
one less than the usual number of leaflets. ‘The importance 
of the petiole position as the center around which the read- 
justment takes place is evident in all cases. At first sight 
one might be inclined to attribute this predominance entirely 
to the coarse obviously mechanical stresses exerted by the 
petiole. The reactions in Lupinus albus, however, cannot be 
explained in such a way. One can very well imagine the 
complexity of the internal factors controlling the configura- 
tion of the leaf system in this case when the removal of the 
leaflet causes such an intricate reaction in a leaf where, on 
account of the rigidity, we should expect very little internal 
rearrangement. Yet even here we find the very complexity 
a valuable aid in determining the component parts of the re- 
action and the results lead us to hope that we may in the 
future be able to get at some of the laws of the correlation. 
For instance, the possibility of obtaining the value of the pet- 
iole factor in so far as it influences the size of the leaflet inter- 
val is certainly of general interest. May we not ina similar 
manner in other organs obtain the relative values of the mem- 
bers in determining the configuration? 
Summary of Method and Results. 
Two coérdinate series of leaves were taken in each of 
three species of plants (Parthenocissus quinguefolia, Trifolium 
pratense and Lupinus albus) and were kept under conditions 
as nearly alike as possible except that in one of the series a 
particular leaflet, the one at the immediate right of the termi- 
nal one, was removed at the earliest possible stage. When 
the leaves had attained their maximum size, measurements of 
the length and angular position of the leaflets in both series 
were taken on the same day. A comparison of the average 
lengths and average positions of the leaflets in the two cases 
gave the change produced as the result of the operation. The 
changes were treated under three heads, changes of position, 
of intervals and of length. 
