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As Hjalmar Nilsson first observed, false wild oats are not completely 

 developed from the beginning. The first year they differ from the 

 cultivated sort only in character of awn. When these first generation 

 types are sown out by themselves they not only reproduce their 

 own peculiar character but produce forms which resemble in character of 

 kernel both the cultivated sort and the true wild species. The experiments 

 continued by Nilsson-Ehle since 1900 have shown that in the production 

 of these forms there is an ordinary segregation in the Mendelian sense, 

 thus proving that mutations act much as do crossings, a fact which often 

 renders it difficult to distinguish between them. In the light of the above 

 observations, the course of development of "false wild oats" is believed to 

 be substantially as follows: Among the ordinary sexual cells arises 

 one which for some unknown reason possesses certain of the wild 



FIG. XIII. "False Wild Oats." 



Signe Nilsson-Ehle del. 



oat characters. It is believed that the alteration in this cell is due 

 to the dropping out or the lapsing into latency of a restraining or 

 inhibiting factor. The absence of the inhibiting factor in both egg 

 and pollen cells allows the typical, fully-developed false wild oat type 

 to arise at once; the presence of these factors in both cells is believed 

 to restrain the development of the characters of the wild oat so that the culti- 

 vated form may arise while the presence of such a factor in only one of the 

 sexual cells (egg or pollen as the case may be) allows the partially developed 

 form to arise. Returning now to the behaviour of this mutating sexual cell 

 (egg-cell or pollen-cell as the case may be) when fertilized by a normal sexual 

 cell, we find that the result becomes to all intents a crossing between them. 

 It is the Fj (first generation hybrids) from this crossing (See Fig. 13, b.) 

 which marks the first apparent deviation from the common oat. When the 

 progeny of F! are sown, about 25% of the plants produced resemble the typical 

 cultivated sort (Fig. 13 a.) and breed true in succeeding generations. About 

 50% possess the character of the type first found (Fig. 13 b.). These are in- 



