132 EXPERIMENT STATION RECORD. [Vol. 40 



The Fi generation proves to be intermediate between the two parents, pro- 

 ducing tubers two or three times as large as the wild parent. The F ; includes a 

 number of individuals apparently identical with the wild parent. Intermediate 

 forms were also obtained, and it may appear that the domestic parent is also 

 represented. The hybrid has been grown at various points, and this material is 

 to be used in further genetic studies. 



Mass mutations and twin hybrids of CEnothera grandiflora, H. Dk Vrtes 

 (Bot. Gaz., 65 (1918), No. 5, pp. S77-J,22. figs. 6).— The author has given atten- 

 tion to the phenomenon reported with discussion by Harriett (E. S. It.. 35, p. 128) 

 under the name mass mutation, which is said to give rise to offsprirfg deviating 

 in large numbers from type in a particular direction and appearing in the same 

 sowings with normal mutations in other directions. Guided by the fact pointed 

 out by Bartlett that the phenomenon bears some resemblance to Mendelian 

 segregation, and proceeding on the assumption that the fundamental mutation 

 possibly occurred in only one of the two gametes in a generation preceding the 

 one in which the diversity becomes manifest, the anther has studied the phe- 

 nomenon of mass mutation in CE. grandiflora in connection with its ability to 

 produce twin hybrids in certain crosses, lie .!aims to have found that the twin 

 hybrids may lie considered as a consequence of mass mutation, the mutated 

 gametes producing one of the twins and the typical sexual cells the other. This 

 conception is considered as applicable to <;:. lamarckiana, rendering superfluous 

 certain hypotheses previously proposed. 



It has been found thai <K. grandiflora from Castleberry, Ala., split* into 

 two types in every generation, one of these consisting of strom:. green plants of 

 the parent type, the other .if weak, yellow Individuals, only a few of which 

 flower and ripen seeds. The latter type is called <]:. grandiflora oehracea. 

 Besides these, it produces other mutants in the ordinary proportions of 0.1 to 1 

 per cent, namely. <K. lorea, with almost linear leaves, and <E. giffOS, with 28 

 chromosomes and the corresponding stoutness of all its organs. These two 

 types are constant from seed, but <!'.. gigai mutates into CE. lorea and '/.'. 

 oehracea. Crosses among '/.'. grandiflora, CE. oehracea, and CE. inn a show that 

 these forms are IsogamiC, the pollen carrying the same hereditary qualities as 

 the egL r cells. Other observations are Indicated with discussion. 



The observed facts and the occurrence of about 25 per cent of barren grains 

 among the seeds led to the conclusion that the yearly production of CE. ochrw 

 is a phenomenon of mass mutation analogous to the Instances reported by 

 Bartlett. and due to an initial mutation of the ordinary rare type followed by 

 secondary mutation in the succeeding generations. This [nitlal mutability of 

 CE. grandiflora Is thought to have yielded, besides the ordinary mutants, hybrid 

 mutants produced by the combination of a mutated sexual cell with a normal 

 one. Assuming the offspring of this fecundation to split in a manner analogous 

 to Mendel's formula for monohybrlds, three types are supposed to result. One 

 of these is the mutant <1'. oehracea, which is now a secondary mutant: the - 

 ond is a mutant hybrid of the type of the species, which will repeat the -put- 

 ting; and the third must be a constant form of the same type. This last d< 

 not appear, and a lethal factor is assumed to account for this gap. It must he- 

 linked to the otherwise pure CE. grandiflora gametes. It is supposed to explain 

 the absence of the constant type, together with the presence of a corresponding 

 percentage of empty seeds. In this way. the mass mutation as well as the empty- 

 grains can be explained by the assumption of two initial mutations of the 

 ordinary type. One is that into (K. oehracea, the other is the origin of a lethal 

 factor linked to the gametes which are not imitated into a weak", yellow form. 



South African Perisporiales.— I, Perisporiaceoe. Knin M. DomOE (Tront. 

 Roy. Soc. So. Africa, 5 (11)17), pt. 6, pp. 713-750, pis. 10).—T\w author presents 



