250 University of California Publications in Botany ["^^ol. 5 



A complete and careful reading of Mrs. Thomas' original paper 

 will go far toward convincing anyone that the occurrence of par- 

 thenogenesis as reported for her cultures «^f Xicotiana is not wholly 

 the result of errors in technique and manipulation. Wellington 

 {loc. cit., p. 288) makes the obvious suggestion that Mrs. Thomas 

 failed to notice adventitious buds which so frequently develop along 

 with the castrated buds under the bag in Xicotiana. Thus he feels 

 that the seed she found was produced not by the castrated flowers 

 but by untreated flowers from adventitious buds which had been 

 originally overlooked. ^Irs. Thomas' report of her experiments 

 certainly leaves much to be desired so far as essential, descriptive 

 detail is concerned. One is. however, convinced that the ordinary 

 precautions to prevent contamination were observed and that noth- 

 ing imperfect or unusual in the method of sterilizing the instruments 

 or trimming or bagging the inflorescences can be claimed. Further, 

 Mrs. Thomas definitely states in her type description of technique 

 that she opened a bag ten days after the castration and pinched off 

 the "one or two tiny buds which were sprouting" alongside of the 

 castrated flowers which had in that time "set seed" (Thomas, loc. 

 cit., p. 2). She thus appreciated the fact that in the ready produc- 

 tion of adventitious buds there was a source of error for her experi- 

 ments. The fact that approximately an equivalent length of time 

 is necessary as well for the development of an open flower from a 

 bud as for the maturing and shedding of seed from an open flower, 

 makes it evident that at least a week and probably three times that 

 length of time would have intervened between the ripening of the 

 seed from castrated flowers and from overlooked, untreated flowers. 

 It is almost inconceivable that ]\Irs. Thomas could have overlooked one 

 or a number of flowers which would probably have been fully open 

 at the time she would have expected the ripened capsules or seed 

 from the castrated flowers to be ready for removal from the plant. 

 Wellington {loc. cit.) also calls attention to the fact that "both 

 self-fertilized and parthenogenetic blossoms produce offspring true 

 to the mother species; and consequently an error, if it did occur, 

 could not be detected." This statement should have little signifi- 

 cance for ]\Irs. Thomas' experiments in that she found seed parthe- 

 nogenetically produced on five distinct hybrid groups in F, and ¥._.. 

 In such material parthenogenetic and self-fertilized seed should, 

 according to current views on heredity, give different offspring. 



