DEPARTMENT OF BOTANICAL RESEARCH. 101 



These cultures of L. decemlineata, reared continuously through 

 many generations under desert conditions, are beginning to shov/ other 

 changes in color, in pattern, in sculpture, and possibh^ in reactions 

 or behavior. Many show slight alterations; some tested in the lab- 

 oratory at Chicago are permanent, others are not so permanent, and 

 the entire series gives one the idea of being subjected to some disturbmg 

 processes that have not yet gone far enough to manifest themselves in 

 pronounced changes or to indicate just what is to be the outcome. 

 Present indications are that in these series of cultures we are observing 

 the effects of the continuous pressure of the medium upon the race. I 

 hope that these lines can be continued long enough to give some experi- 

 mental basis for opinion upon this problem, and unless some accident 

 happens the present equipment renders the prospects for this much 

 greater than in previous years. 



The mutating stem stocks noted in previous reports, although 

 largely reduced by the winter's elimination, so that the surviving 

 populations were all close to the mode of the group, have continued 

 to show the production of mutants in each generation, one that 

 appeared being a further alteration of one that had previously been 

 obtained. This series of cultures and its mutant products have now 

 been sufficieittly tested with regard to their production in nature at 

 Tucson and in the laboratory at Chicago to determine the type of 

 behavior and its method of production. Six more of the mutants have 

 been subjected to genetic testing and analysis during the past year at 

 Chicago, so that the constitution of several of them is now partly known. 

 None of these have so far shown any new gametic agents, the mutants 

 in every instance being due to combinations of agents that entered into 

 the original stem stock from the parental species. Although no new 

 gametic agents have been discovered, and maj'^ not be produced by this 

 process, it is obviously one that, operating in nature, would produce 

 no end of heterogeneity and give an opportunity for the establishment 

 of independent new specific groups. 



Within the last three years a new inheritable type of modification has 

 appeared, which concerns fundamental alterations in the stripes upon 

 the elytra, of a kind and extent not known in any of the original species. 

 This series of changes, which now are found in nearly all of the mutating 

 stem stocks, arises slowly by small variations and in many respects 

 seems to be due more to environment than to the mutating process 

 which the stocks show, although it is not possible in this series to dis- 

 tinguish clearly the causes. 



Cultures of these elytral modifications tested in the laboratory at 

 Chicago show complete genetic stability, a high degree of dominance 

 over the normal, and (what is more interesting) a sort of orthogenetic 

 progression, simpler conditions being followed even in pure lines by 

 more and more complicated conditions of pattern arrangement. 



