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themselves around the mean in accordance with the "Law of Quetelet." 

 Certain of those constituents which deviated farthest from the mean in regard 

 to certain characters, were selected and propagated separately but instead 

 of producing a progeny identically similar to the mother plant in each case, 

 they showed a regression to the original type of the line. Extensive experi- 

 ments finally induced Johannsen to conclude that continuous selection 

 within pure lines is unable to produce permanent changes. In other 

 words, he concluded that there is no hereditary variation within pure lines, 

 and therefore no possibility of effecting permanent improvements in a self- 

 fertilizing race by means of such variation. He did succeed, however, in 

 isolating an occasional product of what he regarded as a "mutation" or 

 sudden variation which appeared as something "new." Should such for- 

 tuitous germinal variations arise frequently it would seem possible to obtain 

 results by careful continuous selection along definite lines. Since however, 

 such variation might be extremely small and neither meristic nor morpho- 

 logical in character, it would be extremely difficult to determine whether or 

 not any definite progress was being made. Only the best statistical methods 

 would suffice and even then the opportunities for experimental error would 

 be such as to render it almost impossible, except perhaps over a long series of 

 years, to form any conclusion which would be above scientific criticism. 

 Up to the present all efforts put forth in Scandinavia have failed to show 

 the utility of continuous selection as a means of effecting improvements of a 

 permanent nature in pure lines. 



Johanneen's work has contributed greatly to our knowledge of selection 

 by revealing the existence of pure lines, biotypes or "genotypes" as he 

 sometimes calls them. He has demonstrated that continuous progress need 

 not be expected by basing selection upon Galton's Law since a population, 

 consisting as its name implies, of biotypes of different means cannot possess 

 a biological mean. The so-called variations of Galton and Darwin, in so far 

 as these concerned self -fertilizing plants, would therefore seem to be simply 

 distinct biotypes which, on being propagated separately, breed true. By 

 avoiding accidental crossing, which even in the so-called " self -fertilizing 

 species" is known to occasionally take place, the constancy of these lines 

 may be fully maintained. These conclusions received much support from 

 the work at Svalof, at which place experience seemed to show more and more 

 conclusively that if hereditary variations did exist in pure lines they were 

 rarely to be found, at least by mere plant inspection. 



Many interesting examples are on record at Svalof of efforts being put 

 forth to find within these pure cultures, the starting points for new and 

 better sorts. Thus, many apparently aberrant individuals were taken out 

 and propagated separately, but in all cases they proved to be mere transient 

 modifications as they failed to reproduce the special characters for which 

 they were selected. In 1900, according to Nilsson-Ehle, an aberrant oat 

 plant which seemed to give promise of marking an advance over its host, 

 was found growing in a certain pedigree culture having the stock-book 

 number 0385. This plant had three kernels in each spikelet, while the sort 

 0385 was characterized by two. The kernels were described in the records 

 as "actually appearing better, more oval, plump and' of better quality." The 



