Journ. of Gen. 13: 79-100 (1923)
The inheritance of glume-length in a wheat cross
F. L. Engeldow

[Excerpt]
To the extent to which hypothetical Mendelian factors in general can be reasonably imagined, it is not very difficult in many of these cases to conceive the possibility of 2, 3, or even 4 factors all controlling a single plant "character." To varying degrees in a number of crosses, the breeding of partial F3, F4 ... generations has supported the multiple-factor hypothesis. This hypothesis evades stringent tests because of its elasticity. The number of factors and their individual potencies can be endlessly varied, and thus made to meet a great diversity of observational requirements. But the more numerous the stipulated factors, the more numerous must be the observations required for the proof of their existence. It is perhaps not unduly cautious to say that investigations relating to multiple-factor inheritance have so far indicated rather than demonstrated the existence of such factors.