DEPARTMENT OF EXPERIMENTAL EVOLUTION. 125 



In spite of this long and continuous parthenogenetic reproduction 

 the Unes seem to be as vigorous as ever. No apparent need for sexual 

 reproduction has manifested itself, for although males have appeared 

 in response to the appropriate environmental influences, sexual repro- 

 duction has not occurred and the lines have continued parthenogenetic 

 reproduction with undiminished vigor. 



Sex in mucors. — -Dr. Blakeslee reports that, in investigations on the 

 common bread-mold, in which he was assisted by Mr. A. F. Schulze, 

 some facts of interest were discovered relating to the distribution of 

 the two sexual races in nature and to the differences between them. 



THE INHERITANCE OF GERMINAL PECULIARITIES. 

 FLOWERING PLANTS. 



Investigations on the flowering plants have been continued by Dr. 

 Blakeslee along the Unes reported on last year. 



In the yellow daisy {Rudbeckia hirta) added evidence has been accu- 

 mulated in regard to the inheritance of self-sterility and self-fertiUty 

 and the effects of inbreeding which tends to bring about incompat- 

 ibihty between sibs, reduced germination, and dwarfed and weakened 

 offspring. It has been definitely established that there are two types 

 of variants with yellow cones. The one turns black, the other bright 

 crimson, with KOH, but they are alike in outward appearance. When 

 these two types are crossed they throw purple cones in the Fi genera- 

 tion, and in the F2 the two yellow types reappear. A repetition of 

 crosses grown in the garden last year indicates that one of our original 

 crosses on wild plants resulted from off pollination and that we have 

 in hand only two instead of three genetically distinct types of yellow 

 cones as reported last year. Investigation of doubling now under 

 way indicates that this character is extremely complex. 



The work on jimson weeds {Datura stramonium) has been extended, 

 and a number of new mutants discovered. One called ''Globe" 

 reported upon last year we have grown for several generations without 

 being able to obtain a hue which breeds pure for this character. The 

 ''Globe" plants can be recognized in the seed-pans and extensive 

 sowings are soon to be made of pedigrees from this mutant which will 

 not be grown to maturity. It is suggested from work already done 

 that the mutant character is transmitted through the female and not 

 through the male parent. 



The type with spineless capsules, slit corollas, and lacerated leaves 

 which was grown last year and provisionally classed as a dominant 

 character has been investigated in some detail. The character-com- 

 plex appears first on the later branches of sUghtly over 1 per cent of 

 the plants in the field from five different sources. When the character 

 is well expressed the stamens contain no pollen. The seeds secured 



