Recent Papers on Qinothera Muiatwns. 29^ 



nuclei (presumably the female) in the fertilized egg ; (ii.) the apparent 

 presence of only 7, the x number of chromosomes, in the cell- 

 divisions of the embryo ; (iii.) the smaller size of the embryo and 

 its cells and nuclei in biennis x inuricata than in biennis, which 

 would be anticipated according to Boveri's law. Nevertheless, there 

 are various difficulties, and the results of a fuller study of the 

 subject will be awaited with interest. A number of other questions 

 remain to be solved. If the hybrid embryo begins its divisions with 

 only 7 chromosomes it is not probable that this number persists 

 throughout the sporophyte, and Goldschmidt believes he has found 

 evidence that the 2x number is restored in the later mitoses of 

 older embryos. This introduces difficulties, however, for it is 

 scarcely probable that all the cells would double tiieir chromosome- 

 number simultaneously, and if both types of cells continued we 

 should anticipate as a result various distortions or changes in the 

 shape of organs, for we should have different chromosome-numbers 

 in different parts of the individual. The manner of chromosome 

 pairing in meiosis would also be of interest, though we might 

 anticipate the formation of seven pairs by analogy with the 

 chromosome behaviour in the tetraploid mutant gigas. If more 

 critical study sustains Goldschmidt's foreshadowing, we shall be able 

 to add one more to the number of cases in CEnothera where cytological 

 research has furnished the key to certain otherwise obscure or 

 inexplicable hereditary phenomena. 



It is worthy of mention that these reversions to one of the 

 grandparents in double reciprocal crosses were predicted by Giglio- 

 Tos (22) on generalized highly theoretical grounds concerning the 

 structure and arrangement of protoplasmic elements, but it is highly 

 improbable that this type of hereditary behaviour will be found to be 

 common even in the genus CEnothera itself. 



If Goldschmidt has correctly ascribed these results to merogony,^ 

 then a similar explanation may be applied (as that author has 

 already done) to the various cases of " false hybrids," such as the 

 well known results of Millardet with strawberries. In this case the 

 hybrids were found to be all purely paternal in character and to 

 breed true. The converse condition known in various Orchids, in 

 which the hybrids are purely maternal in type, may conceivably 

 result from the degeneration of the male nucleus after entering the 

 egg or, as has often been suggested, from stimulation of the egg to 

 parthenogenetic development by the presence of the pollen-tubes. 



Another series of interspecific crosses has been made by Davis 

 (7, 8, 9). He chose races of 0. biennis from Massachusetts and of 

 0. grandiflom from Alabama for the parents of his crosses, in the 

 hope of producing O. Lamarckiana. But it must be said that from 

 this point of view the results have not been successful. Hybrid 

 forms were obtained, some of which showed a certain amount of 

 crinkling of the leaves, but that is only one of many features of O. 

 ■ Since the above was written, Renner (" Uber die angebliclie Merogonie 

 der CEnotlierabastarde," Ber. d. deutsch. bot. Ges,, Bd. 31, pp. 334-335, 1913) 

 has re-investigated the subject in 0. muricata x 0. biennis, 0. biennis x 0. 

 Lamarckiana and 0. Lamarckiana x 0. biennis. He finds the usual double ferti- 

 lization in all cases, with 2x chromosomes in embryo and endosperm. Re- 

 examination of Goldschmidt's preparations leads to the same result, so it must 

 be concluded that there is no evidence for the theory of merogony in these 

 hybrids as expressed by Goldschmidt. 



