III. THE OCCURRENCE OF PARTHENOGENESIS. 



The question of parthenogenesis in N. tabaciun was taken 

 up in consequence of a paper pubhshed in the Mendel Journal.^ 

 In this communication the author stated that she had been able 

 to obtain parthenogenetic seed with the greatest ease in the case 

 of N. sylvestris, N. tabaciim, N. siiavolens, N. sandera, and 

 hybrids from these. In some cases only the anthers were 

 removed, but in others both anthers and stigma, Avhile the 

 ordinary precautions of sterilizing the instruments and enclosing 

 the flowers in wax-paper bags seem to have been scrupulously 

 observed. Success did not attend all the experiments, but 

 " parthenogenesis was discovered in ten species, varieties and 

 hybrids of Nicotiana on chosing the right period for trial, ^.e., 

 when the plant is beginning to go off its fullest bloom. In the 

 tabacums success was unfailing." East" also mentions the 

 possible production of apogamous seed. " In crossing species 

 of the genus Nicotiana I have had plants develop from seed 

 that have apparently been formed apogamousl}^ that is, formed 

 from an immature egg-cell without fertilization. It is evident 

 that this is induced by the extraordinary irritation of foreign 

 pollen." 



Experiments were undertaken both in 1910 and 1911 to 

 determine whether, under the conditions obtaining in Pusa, 

 N. tabaciun will set seed without pollination. It had already 

 been observed that castrated flowers prepared for hybridization, 

 which owing to pressure of work or other reasons had not been 

 pollinated, invariably dropped without setting any seed. In 

 order to obtain more definite information on this point, a large 



1 Haig Thomas, The Mendel Joimml, No. 1, 1909. 

 » East, The Popular Science Monthly, 1910. 



