8 BOTANICAL GAZETTE [july 



obtained from seeds has been in some cases too small for entirely 



satisfactory results. 



The Oenothera and Hieracium hybrids mentioned may be said to 

 resemble each other in that in both the F^ is heterogeneous, though 

 the types of which the Fj is composed differ in the two crosses, 

 agreeing only in that one of the types in each is the pure mother parent. 

 The abortive character of the pollen in O. lata may also be said to 



■ 



favor rather than otherwise the probabihty of apogamy in this species, 

 as it is well known that apogamous species frequently do not mature 

 their pollen. This suggestion of apogamy in O. lata will be examined 

 in another light in connection with the discussion of the number of 

 chromosomes. 



Millardet's'^ ^' false hybrids'* in Fragaria and Rubus, in which 

 only one of the parent types (usually the mother) is produced in the 

 hybrid, and this breeds true, may possibly be regarded as extreme 

 cases of the same type of hybrid as some of the Oenothera crosses. 



Hurst/ ^ among a large number of crosses of orchids which 

 showed many types of hybridization, found eleven crosses between 

 different genera in which only one of the parent types was reproduced, 

 this being in every case the mother (p, 104). Large numbers of the 

 hybrids were grown in some cases. He concluded that in at least 

 eight of these ^' false hybrids" self-pollination was impossible, and 

 that the embryos probably developed apogamously, perhaps on 

 account of the stimulus from the presence of foreign pollen tubes in 

 the ovary, but without fertilization. Oenothera itself may produce 

 hybrids of this type. Thus DeVries found that O. Lamarckiana 9 

 XO. biennis 3 gives only O. biennis in the F^ and F^ (/• c. 2:31). 

 This cross made in the New York Botanical Gardens, however, gave 

 in addition to several O. Lamarckiana plants, which MacDougal^^ 

 thinks probably came from foreign Lamarckiana pollen, four types, 

 none of which were the same as either parent. Thus entirely different 

 results may be obtained under different conditions. 



i^ Mn^LARDET, M. A., Note sur rhybridation sans croissement ou fausse hybrid- 

 ation. Mem. Soc. Sci. Phys. et Nat. Bordeaux IV. 4^347-372. 1894. 



^' HiTRST, C. C, Notes on some experiments in hybridization and cross-breeding. 

 Jour. Roy. Hort. See. London 24:90-126. figs. Q-41, 1900. 



13 MacDougal, D. T-, Mutants and hybrids of the Oenotheras. Publ. 24, Car- 

 negie Institution, Washington, pp, 56. pis, 22, 1905. 



