DEPARTMENT OF EXPERIMENTAL EVOLUTION. 103 



SO due. However, through lack of a cytologist, we have not been 

 able to test this hypothesis upon all of our mutants. We have merely 

 been able to observe their origin and inheritance but not yet to induce 

 them nor to study their cytological basis. 



Variegation in Lychnis and the Chlorophyll Factors, by G. II. Shull. 



In 10 families derived from crosses between sibs, albinos have con- 

 stituted almost exactly one-fourth of the offspring, the total numbers 

 being 713 green to 240 albino. As many other sib-crosses in the 

 same stock have produced only green offspring there can be no doubt 

 that this result is due to the existence of a fundamental Mendelian 

 factor for chlorophyll-production. 



Two light-green races of Lychnis dioica have been discovered, each 

 of which is recessive to the ordinary dark-green strains. When mem- 

 bers of these two light-green strains are crossed together their Fi off- 

 spring are uniformly dark green. In the Fj, which has been grown 

 extensively this year, the light-green types reappear in approximately 

 the expected ratio, 9 dark : 7 light. It is not certain what should be 

 the result when the determiners for both of these pale races are 

 absent, and it is possible that this ratio should be 9 : 6. Extensive 

 back-crossing upon the pale types must decide this question, and the 

 necessary crosses have been made for this purpose. 



The study of several kinds of variegation has been continued, and 

 material has been secured for testing the results of breeding from 

 variegated males possessing a type of variegation which has proved 

 to be readily transmissible through the seed-parent, but whose effect 

 through the pollen-parent is as yet unknown. A golden variegation 

 discovered two years ago was found to be slightly inheritable through 

 the male as well as strongly inherited through the female. 



Ascidia in Fraxinus, by G. H. Shull. 



In continuation of his experiments recorded at page 88 of Year 

 Book No. 11, with the pitcher-leafed ash. Dr. Shull reports that the 

 two pedigrees representing crosses between a normal and a pitcher- 

 leafed ash, and between two abnormal (i. e., pitcher-leafed) ash trees, 

 have together produced about 40,000 leaflets this year, each of 

 which has been carefully examined for pitchers, and its position and 

 the character of the ascidium, if present, recorded. The cross between 

 normal and abnormal, which produced no abnormal leaflets during the 

 first season following the germination of the seeds, has this second 

 season displayed ascidia on 26.9 per cent of the trees, and in the 

 family produced by crossing two ascidiate trees pitchers have devel- 

 oped on 58.7 per cent of the trees. A still larger percentage of 

 abnormal trees may be expected as they grow older and become more 

 vigorous, and it will not be surprising if in the end there should appear 



