70 

 The Origin of Aberrant Forms as "Mutations." 



"False Wild The appearance in cultivated oat sorts of what has come to be known 



in Canada as "False Wild Oats" has been a matter of common observation 

 in Scandinavia for many years. These aberrant forms have been found 

 both in black and white-grained sorts. Their seeds bear long twisted and 

 bent awns and possess the sucker mouth and hairy callus of the true wild 

 species, but in form and shape the kernels correspond with the variety in 

 which they are found, a fact which often provides a means of distinction 

 between them and true wild oats. The plant of "false wild oats" more- 

 over, does not correspond with that of the true wild species, but is an exact 

 counterpart of the cultivated sort. The plant of true wild oats is usually 

 more luxuriant in growth and more drooping and spreading in habit, and 

 usually stands above the common sorts. The plant rather than the seeds, 

 is therefore accepted as a safer basis of distinction. The origin of these 

 forms has long been a matter of speculation. The close similarity between 

 their seed and that of the true wild species in respect of awn and sucker- 

 mouth development has led to the common belief that some relationship 

 exists between them. On the other hand, the close similarity between the 

 form of the seed and character of plant of the former with that of the culti- 

 vated sort in which it is found has led to the conclusion that the common 

 cultivated sort is also in some way concerned. That these forms do not 

 arise through crossing with the true wild form is shown by the fact that the 

 latter is not found at Svalof, neither is it in any case used in artificial crossing 

 work. That false wild oat types might arise through a peculiar combina- 

 tion of units is likewise untenable, since the segregation of the heterozygote 

 the form usually noted as the first deviation from the cultivated type always 

 displays the simple Mendelian proportions, viz.: 1:2:1. 



Furthermore, false wild oats found in a common side oat, such as Black 

 Tartarian would, in the second generation, divide into side and branching 

 types if they arose as crossings between the above type and the branching 

 wild oat type, A vena fatua. This they do not do. 



Extensive investigations covering several years have been made with 

 these forms at Svalof, the final results of which have only recently been pub- 

 lished (55 p. 1-37). According to these investigations the so-called false wild 

 oat corresponds more closely to what De Vries defines as a Retrogressivemutation. 

 It will be remembered that the above founder of the mutation theory, de- 

 fined two classes of mutation viz: Progressive or positive and Retrogressive 

 or negative. A progressive mutation according to De Vries owes its existence 

 to the acquisition a new unit ; a retrogressive mutation, on the other hand, 

 is supposed to arise through the latency of a unit. Without stopping to dis- 

 cuss this theory here, suffice it to say that no undisputed case of progressive 

 mutation in the sense of De Vries has yet been .found at Svalof. Retrogres- 

 sive mutations representing spontaneous changes from the dominant to the 

 recessive character of a given Mendelian character pair are believed on the 

 other hand, to occur occasionally. The occurrence of False Wild Oats is 

 believed to be due to such a change. 



