F. Kekble 183 



intermediate forms must oecessarily be large, and these forms must also 

 produce the illusion of a continuous series rather than of a series made 

 up of a large but definite number of forms, each of definite constitution 

 and each therefore distinct from the others in genetical behaviour (c/. 

 Nilsson-Ehle (1909) and Baur (1911)). 



Mendelian analysis thus leads to the recognition that just as with 

 antirrhinums, peas, sweet-peas and hosts of other cultivated plants, so 

 with Primula sinensis we have to deal with giants, dwarfs and middle 

 races. 



The case already described in which giants arose as the outcome 

 of the mating of non-giants is at once intelligible when this fact is 

 grasped. Two instances of the appearance of giants in this manner 

 are recorded in Table VII. In one, Snow Drift x Snow King a 

 doubtful (i^„) giant yielded an F.. of 5 non-giant : 2 giant ; in another, 

 an F-i from Snow Drift x White Queen Star, the ratio is 16 (? 17) non- 

 giant : 1 (? 2) giant. 



Now although both Snow King and White Queen Star are alike 

 in their stellata flowers and steUata habit of inflorescence, the flower 

 of Snow King is distinctly larger and the petals more massive than is 

 the case with White Queen Star. In other words Snow King is a 

 semi-giant. It must therefore contain more of the factors for gigantism 

 than are borne by White Queen Star. 



By ascribing factorial formulae consistent with their apparent con- 

 stitutions 10 the varieties Snow Drift, Snow King and White Queen 

 Star it is possible to account for the several results obtained by crossing 

 each of the two latter varieties with the former variety. 



Thus and by way of illustration only, if the constitution of Snow 

 Drift be aabbCC and that of Snow King be AABBcc then 



Snow Drift x Snow King 

 = aabbCC x AABBcc 

 and F, = AaBbCc 



F.2='3 giant and giant-like : 61 non-giant 

 = 3 „ :61 



as compared with 1 „ : 15 „ found 



= 4 „ :60 „ 



A further point worth bearing in mind is that the conception of 

 three factors admits of the explanation of minor but constantly recurring 

 variations in shape and size of flower. For in a family which lacks the 



Journ. of Gen. n 13 



