i8 PLANT-BREEDING 



The association of characters is often called correlation. 

 It may be an accidental or a normal coincidence of charac- 

 ter-units. But more often the same simple character mani- 

 fests itself in different parts of the organism (as, for instance, 

 in the color of flowers, berries, seeds and foliage) and thereby 

 affords a means of investigating it. Of late, such associa- 

 tions have become of high importance, since selection may 

 be guided by them. Especially, in the isolation of new var- 

 ieties of cereals has this use proven very valuable. Our 

 fourth chapter will deal with these Ciuestions. 



For the direct observation of the process of mutating, the 

 evening primrose of Lamarck affords, at present, an un- 

 equaled opportunity. It produces numerous mutants, and 

 does so in every generation, and almost any sample of pure 

 seed may be used for this study. This species was described 

 by Lamarck, from specimens of the l:)otanical garden at Paris, 

 a century ago. It seems to have since been lost. It was 

 re-introduced into European garden-culture, about the mid- 

 dle of the last century, by a nurseryman in London, who 

 received the seed, without name and in a mixed packet, cul- 

 tivated and multipKed it and sold it to the leading firms on 

 the continent. All the strains derived from this scource 

 show the same phenomena of mutability, as far as my experi- 

 ments go. Where the species is growing in America in the 

 wild condition, is not known, at present, and so it is impossible 

 to decide whether it has acc^uired the habit of mutating in 

 that condition or upon its introduction into European culture. 



Twenty years ago, I found this species on a waste field 

 near Hilversum, in Holland, where it had escaped from culti- 

 vation and was rapidly multiplying itself. Here it had pro- 

 duced two new and distinct varieties which, up to the present 

 time, have not been collected or observed elsewhere. One 

 of them had smooth leaves, lacking the bubbles of the ordi- 

 nary form; it was a fine type with narrower leaves and petals, 



