262 University of California PuhUcations in Botany [Vol. 5 



Partial List op Species and Varieties Used in Testing for Parthenogenesis 



A description of them is to be found in Professor Setchell's paper (1912). 

 Nicotiana Tabacum "Brazilian" Nicotiana rustica (seven varieties) 



Nieotiana Tabacum "Cavala" Nicotiana Langsdorfii 



Nicotiana Tabacum "Maryland" Nicotiana paniculata 



Nicotiana Tabacum var. cah-cina Nicotiana alata 



(Nicotiana Tabacum) "White Tobacco" Nicotiana acuminata (three varieties) 

 Nicotiana Tabacum var. macrophylla Nicotiana Bigelovii 



Nicotiana angustifolia Nicotiana sylvestris 



Nicotiana Tabacum var. macrophylla Nicotiana tomentosa 



purpurea 

 "Nic. tabaecum Cuba"- Nicotiana glauea 



* Described in this paper but not in Setchell (1912). 



The total number of flowers involved in these various efforts to 

 produce parthenogenetic seed is well over 1500 and the number of 

 plants concerned over 450. In not a single instance was any seed of 

 any sort produced, and only very rarely did the capsules remain 

 attached for over two weeks and when, in a few cases, thev did 

 persist the result Avas a shrunken, misshapen capsule containing nothing 

 but the driecl-up ovules in their entirely immature form. The falling 

 of castrated flowers in such experiments on Nicotiana species is very 

 striking. Howard (1913) well describes the difference in this respect 

 between the result of self- or cross-pollination and the result of 

 castration : 



A great difference was found between the capsules formed from castrated 

 flowers and those formed by ordinary pollination. In the latter case the 

 capsule remains firmly attached to the plant. No difficulty is experienced in 

 removing or replacing bags, and the peduncle would have to be broken before 

 the capsule could be removed. This is always the case whether the flowers be 

 self- or cross-pollinated. The capsules of the castrated flowers, on the other 

 hand, although they also become swollen at first and simulated the fertilized 

 ones, were very easily detached from the plant. It was exceedingly difficult 

 to remove the bags, which finally had to be cut away carefully. The capsules 

 thus exposed to the air were easily blown or knocked off. 



Wellington (1913) has given a detailed summary of the literature 

 dealing with the problems of parthenogenesis on the plant side, and 

 no further review of it need be given here. I wish, however, to call 

 attention to two additional references which are of particular interest 

 here. First the experiments of Howard referred to above, which are 

 detailed as a preface to the description of breeding experiments with 

 51 varieties of N. Tahacum. The experiments in castration and muti- 

 lation included considerably over 5000 flowers and some apparently 

 parthenogenetic seed was produced. Second, the experiments of 

 Hartley (1902) with tobacco, which are especially important in con- 



