DEPARTMENT OF BOTANICAE RESEARCH. 59 



fraternal group of well-pedigreed cultures was divided into three portions ; 

 one was sent to Tucson and reproduced under the conditions of the moist 

 midsummer of 1910; a second was placed under experimental conditions at 

 Chicago, which duplicated in average intensity and daily range the chief 

 environmental factors at Tucson ; a third was kept in the normal conditions 

 to which the strain had been accustomed for many years. The result was 

 the production of identical modifications in the experimental cultures at Tuc- 

 son and at Chicago, and the non-modification of the group which was allowed 

 to breed under normal conditions. The culture at Tucson passed the winter 

 of 1910-1911 in hibernation and the count of the material in the spring of 

 191 1 showed 66 unmodified and 115 modified. In the Chicago portion of 

 the experiment essentially the same proportion of the culture was changed, 

 and these on further breeding have proven to be inheritable variations. Dur- 

 ing this time the main stock, as well as the control culture, has not shown the 

 least trace of the modifications produced in the two experiments. It is of 

 interest to obtain in the same homogeneous material the same results in 

 experiments, in nature and in the laboratory. 



One of the first lines of investigation started at Tucson was the effort 

 to create and maintain a race which should mutate in the manner of O. 

 lamarckiana, and then to determine the relation of the extent and frequency 

 of the mutations to the variation of the environmental conditions of the cul- 

 ture. It developed early that apparently similar races could be produced if 

 freely inbreeding species were allowed to inbreed at liberty, and that the out- 

 come was, in the huge majority of instances, the production of a stable race 

 that at intervals gave sports, which were the reappearance of the attributes 

 entering into the original combinations. Several such combinations were 

 made at Tucson in the beginning, and in the earlier years these speedily 

 settled down to a stable type with the normal fluctuating variability. These 

 combinations are no more prone to wide variation than are the natural spe- 

 cies, and under fairly constant conditions continue to breed true at Tucson 

 and at Chicago, whence some of them have been taken to be tested. 



In the years 1910 and 191 1 some of these cuhures have been tested to 

 determine the role that changing or intensified conditions would have in the 

 production of rh3'thmic mutability. In the tests each culture was divided, 

 and part was tested and part kept under normal conditions. In all of the 

 cultures it has thus far been the experience that the experimented culture 

 has given an increased variability and in all cases a greater or less array of 

 mutants. One of these tested cultures has given, under the intensified condi- 

 tions, an increased mutability, generation after generation, in much the same 

 manner that O. lamarckiana does. One of the most interesting of the cul- 

 tures has given, in the two generations of 191 1, types that are recombinations 

 of the attributes that went into the original combination, and some of these 

 had not been present in the hybrid combination or in the parent stock for 

 ten or more generations. The general outcome of these experiments at Tuc- 

 son and in other locations indicates that we are dealing with a potent means 



