1919] Frost: Mutation in Matthiola 159 



SUMMARY 



This paper describes the occurrence, characteristics, and heredity 

 of certain aberrant plant types which decidedly resemble some of the 

 "mutant" types produced by Oenothera lamarckiana. The parent 

 form is Matthiola annua Sweet, of the horticultural variety "Snow- 

 flake." 



These aberrant forms may be called mutant types, since it is highly 

 probable that they are originally produced by mutation. The aberrant 

 individuals may be termed apparent mutants, since it may be con- 

 sidered uncertain whether they usually arise by immediate mutation 

 or by segregation. The case acquires special significance because indi- 

 viduals belonging to the mutant types, although the species is known 

 to be typically Mendelian with respect to various characters, give 

 erratic heredity ratios sugge.stive of Oenothera. 



At least eight types have been somewhat carefully studied, and six 

 of these have shown their heritability in progeny tasts. Several other 

 types have been named, but for various reasons their distinctness is 

 more or less doubtful. 



Some of the commoner types have each been produced by many 

 parents, and in several pure lines isolated from the original com- 

 mercial variety. The apparent mutants other than the early type com- 

 pose about four or five per cent of the progeny of Snowflake and early 

 parents, the separate types ranging down from about one per cent. 



Most of the mutant types are in general inferior to Snowflake in 

 vigor, and the difference in development is greatly increased by certain 

 unfavorable environmental conditions. The proportion of apparent 

 mutants in cultures from Snowflake parents appears to be definitely 

 lower where germination is comparatively poor. 



The mutant types differ from Snowflake and from each other in 

 various respects. The early type is practically a smaller and earlier 

 Snowflake. The other mutant types, on the other hand, differ markedly 

 from Snowflake in vigor, fertility, and various form and size char- 

 acters. Each type is named from some conspicuous characteristic 

 difference from Snowflake. but usually various other differences can 

 readily be found. 



Somewhat extensive progeny tests have been made for five of the 

 mutant types, and a little evidence secured for two or three other types. 



