SUMMARY OF SECTION. 107 



The operation of this law is to be seen in other of the morphogenetic 

 activities of the plant than those which liave been discussed in this 

 section. In a later section data are given showing that it holds in branch 

 production. It seems to me that a number of results obtained earlier 

 in the paper can best be interpreted as due to the operation of this law. 

 Thus, in examining the data on which our first law of growth was based 

 it was found that the slope of the positional regression line was steepest 

 for secondary-branch whorls, less steep for whorls on primaries, and 

 had the least slope in the case of main-stem whorls. It was pointed 

 out in the discussion that this meant that a given type was attained 

 with the production of fewer whorls in secondary than in primary 

 branches, etc. Similarly it appears probable that the diminution in 

 variability with successive whorl formation goes on more rapidly the 

 farther distad on the plant we go. That is, the same rule appears to 

 hold between different axial divisions of the plant as holds for the organs 

 within a given division. In other words, as we go towards the periphery 

 of the plant the variability of repeated characters diminishes in such a 

 manner as to give the impression that in some way there is stored up 

 in the protoplasm, as it were, the results of previous morphogenetic 

 experience. An axillary bud on a primary branch goes through the 

 same series of events when it develops into a branch as does an axillary 

 bud on the main stem. It produces whorls whose type changes accord- 

 ing to a logarithmic law, and whose variability diminishes with successive 

 formations. But the rate at which it attains any given result in this 

 series is greatly accelerated over that at which affairs went on in the 

 case of the bud on the main stem. The formative activities of each 

 bud on the plant appear to be influenced in some very direct way by the 

 sum total of previous morphogenetic history of the portion of the plant 

 proximal to the bud. That the two things are objectively related is a 

 fact clearly demonstrated by the results which have been presented in 

 this and earlier sections of the paper. No one who will take the trouble 

 to study carefully these results can fail to be impressed with the reality 

 of the fact, I think. How such a relation as that of which we are 

 speaking is to be interpreted or explained is another question to which 

 we shall return in the concluding section of this paper. 



The relation of this second law of growth to our earlier results on 

 the variation in whorls on different axial divisions of the plant is so 

 obvious as hardly to need special mention. In connection with the first 

 law of growth it enables us to interpret very clearly and completely the 

 results regarding variation obtained from grouped material. Thus, for 

 example, it was found that main-stem whorls as a class are least varia- 



