54 University of California Publications in Agricultural Sciences [Vol. 2 



tiou is typically ehalazo^amous, there being a well-developed bi- 

 nucleate cell which reaches the embryo sac. Hence the occurrence 

 of reduction may be assumed, in which case embryos must arise 

 through apogamy in the absence of fertilization. But with the 

 haploid number of chromosomes in the somatic tissue of these 

 seedlings, as v^nll be shown below, one might expect even greater 

 deviations from the parent forms than actually occur. Thus, 

 if apogamy and reduction be assumed, it seems necessary also 

 to assume'^ "the subsequent arrest of the homotypic mitosis 

 (in the cell destined to diiferentiate the embryo sac) before the 

 division of the nucleus has taken place, resulting in the pro- 

 duction of a functional germ cell with a chromosome number 

 double that of its reduced number. ' ' 



Regarding the other question, the mutations that produce 

 quercina seedlings evidently occur only in pistillate calif ornica 

 flowers, thus producing seedlings that will not breed true. This 

 indicates that the cytological time of mutation is previous to 

 fertilization. 



From her cytological studies of CEnothera Lutz^* has con- 

 cluded that "all individuals of a given type of vegetative char- 

 acter invariably have identical somatic chromosome numbers 

 regardless of the diversity of origin of the individuals in ques- 

 tion," and, further, that "All individuals . . . having a chro- 

 mosome number much in excess of that in 0. Lamarckiana dis- 

 played certain characters strongly suggesting those of 0. gigas, 

 chiefly noted in the stoutness of all parts." This suggests that 

 in a form like quercina, which is reduced in all vegetative char- 

 acters, we should expect to find the somatic number of chromo- 

 somes to be less than the number typieal of the species. 



The occurrence of such a mutation in Juglans is of especial 

 significance because of the phylogenetic relationships ascribed 

 to these chalazogamous forms. According to Nawaschin and 

 Finn,^^ the preservation of the male cytoplasm in the species of 

 Juglans indicates an old tendency inherited from gymnosperm 

 ancestors and furnishes further important proof of the great age 

 of these forms, which stand on the threshold of the angiosperm 

 world. Berry^^ mentions the occurrence of seven species of 

 Juglans in the upper Cretaceous deposits, twenty-five in the 



