64 Mutations and Evolution. 



From a study of the early records, Miyoshi concludes that a 

 large number of cultivated sorts existed two centuries ago, and 

 has been largely added to during the last hundred years. The 

 many forms which receive botanical names for the first time are 

 distinguished by such features as leaf colour, flower colour, singles 

 or doubles, fragrance, inflorescence, and pubescence. The 

 multiformity of the group is comparable with that of the North 

 American Crataegus, or with Draba verna or Viola tricolor, and 

 the forms appear to have arisen as mutations. Seeds in most 

 cases yielded a uniform offspring, but it seems possible that some 

 mutational characters may have been transferred by crossing. 

 Peloria. 



Peloria, or the sudden development of actinomorphic flowers 

 in a zygomorphic species, has been studied most extensively in the 

 Scrophulariaceae where it occurs most commonly, although it is 

 also found in the Labiatae, Leguminosae, Orchidaceae and other 

 families with zygomorphic flowers. It is of evolutionary interest 

 because zygomorphy is supposed to have been gradually developed 

 in relation to the visits of insects, while peloria is a sudden 

 re-expression of symmetry. 



Peloria behaves in part as a recessive character, is known to 

 occur as a variation in numerous wild species, and in a few cases 

 has become a specific character, indicating that in such cases 

 zygomorphy is not essential for survival. De Vries ' studied 

 peloria in Linaria vulgaris for thirteen years and gives the 

 literature of the subject up to the time of his work. He mentions 

 Mentha aquatica as a species whose apical flowers are always 

 peloric, and Uropedium Lindenii, found in Colombia, as the peloric 

 form of Cypripedium caudatum. It is not impossible that the 

 Ranunculaceous genus Aquilegia, with its five spurs, arose as a 

 petoric mutation from a zygomorphic one-spurred ancestor. The 

 increased number of nectaries should give it an advantage as 

 regards insect visits. 



The genetical studies of peloria appear to have been confined 

 to the Scrophulariaceae, but in this family the genera Linaria, 

 Antirrhinum and Digitalis have given valuable results. The earliest 

 difcovery of a peloric condition in Linaria vulgaris was made by 

 Zioberg in 1742. On an island near Upsala he found among the 

 normal a plant bearing only regular flowers, and Linnaeus described 

 it under the name Peloria. There are numerous later records of 

 1 The Mutation Theory, Vol. II. 



