DEPARTMENT OF BOTANICAL RESEARCH. 75 



stable, unless subjected to conditions of experiment which induce the 

 mutating behavior. During the past year we have further tested the 

 constancy of these mutant forms and find that they are in the main 

 entirely homozygous, and are constant even in massed cultures. The 

 stem stocks continue to throvv^ of!" the mutant types in small numbers, 

 and these are being tested at Tucson and also at Chicago. 



One culture gave a reaction during the past year that was of much 

 interest. It went into hibernation at the end of 1912, and did not 

 come out at all during the season of 1913, although they were given 

 every opportunity in the way of conditions to do so, but they remained 

 in hibernation until June 1914, when they emerged and gave a strong, 

 fairly numerous progeny, with many mutant types. It is not at all 

 uncommon for some of these forms to remain in hibernation through a 

 year or more, when the environic conditions are severely adverse, but 

 why they should remain in hibernation throughout a season when the 

 conditions were not adverse but favorable is difficult to explain. 



In addition to the mutant types that are thrown out in these cultures, 

 most of which are new or recombinations of factors known to have 

 entered into the original combination, the cultures as a whole show two 

 general reactions to the conditions at Tucson that are of considerable 

 interest. As a whole they are showing a loss of color-forming capacity 

 in both the melanoid and lipoid pigments, giving the cultures a dis- 

 tinctly albinic aspect. This, tested in the laboratory at Chicago, is 

 entirely a recessive character when crossed with the normal stocks at 

 Chicago. 



A second point of interest is the gradual development in successive 

 generations of changes in the factorial composition of the elytra, giving 

 new pattern arrangements not hitherto known in any of the species 

 from which these experimental series were derived. It is not possible 

 to say at present whether this progressive development of new factors, 

 or of arrangements of factors, is due to the environment or to some 

 series of reactions going on within the gametic material which may be 

 independent of the environment or possibly influenced and driven by 

 the environmental conditions at Tucson. These changes are gametic 

 and stable, but further statements with regard to them must be post- 

 poned until test experiments now in progress have been completed. 



In general, this series of experiments seems to be in every respect a 

 confirmation of de Vries's mutation behavior, as observed by him in 

 Oenothera, with the added showing of how the behavior may be pro- 

 duced. It does not follow that this is the only manner in which the 

 same behavior could be produced. By the end of another season or in 

 two at the most it will be possible to give some exact statements of the 

 factorial composition of these mutant types, and of their relations to the 

 original component species. 



