

• 



191 7l CURRENT LITERATURE 83 



nations involved in ordinary Mendelian phenomena; that the mutative changes 

 concern various characteristics of the plant, but that the factor for each new- 

 type is regularly inherited as a unit, sometimes showing linkage with another 

 factor pair, so that we may suppose, in some cases at least, that the essential 

 change is limited to a portion of one chromosome. The very first test of these 

 conclusions would demand that the mutations reproduce the mutational type 

 in 75 per cent of their progeny in the first generation, and that 25 per cent of 

 the progeny be homozygous dominants. This condition apparently is satisfied 

 in the case of only 1 mutation of the 8, and until the data appear we have no 

 basis for an independent judgment as to whether the progenies of the second 

 generation were large enough to prove the point at issue. Except from this 

 one mutation, no homozygous mutational type has segregated from any of the 

 supposed heterozygous dominants. In the mind of one who is familiar with the 

 group of the evening primroses a suspicion naturally arises that Frost's muta- 

 tions are not Mendelian at all, but that they show the type of behavior familiar in 

 Oenothera lata DeVries, and recently discovered in mutations from O. stenomeres 

 and O. pratincola. These mutations always give progenies consisting of a mixture 

 of the parental and mutational types. In the case of 0. lata the cytological 

 explanation is now so well known as hardly to require comment; it certainly 

 suggests that a cytological examination of the Matthiola mutations would not 

 be amiss. Reciprocal crosses between the mutational and parental types 

 might also throw light on the possible analogy between the evening primroses 

 and stocks, for in such types as Oenothera lata mutational characters are 

 carried only by part of the female gametes, and by none of the male gametes. 

 All that Frost tells about the Matthiola mutations so exactly parallels what is 

 found in Oenothera that one can hardly refrain from suggesting, in the absence 

 of data supporting his own interpretation, that instead of discovering new 

 Mendelian dominants he has found in a widely distant group some of the per- 

 plexing phenomena which critics of the mutation theory persist in regarding 

 as peculiar to Oenothera. More and more facts are coming to light in groups 

 other than Oenothera which do not fall into line according to Mendelian expec- 

 tations. As an example of what looks like mutation in the DeVriesian sense, 

 one thinks of the rogues of peas, investigated by Bateson; as an example of 

 matroclinic, non-segregating hybrids, quite comparable to those of Oenothera, 

 we have the cases in Primula, recently reported by Pellew and Durham. 

 If the type of heredity shown by Oenothera lata were found to apply to the 

 mutations of Matthiola, it would be almost as interesting as the discovery of 

 new Mendelian dominants. — H. H. Bartlett. 



Respiration in succulents. 



exhibit 



in their respiratory processes and periodic changes in acidity with light and 

 darkness has been known for a long time. Richards* has investigated these 



* Richards, Herbert M., Acidity and gas interchange in cacti. Carnegie 

 Inst., Washington, Publication no. 209. pp. 107. 1915. 



