184 Gigantism in Primula sinensis 



C factor, one of the other factors may be present in homozygous condition 

 in some members and in heterozygous condition in others. In such a 

 family, which can never produce a giant form, the constituent individuals 

 may be characterised according to their respective factorial constitutions 

 by different modes of growth of the corolla and other parts. In the 

 variety Mont Blanc Star for example there are to be met with constantly 

 plants which bear smaller flowers than the type. These peculiar flowers 

 are characterised not only by their smaller size but also by the fact 

 that the basal parts of the petal-lobes are more fused with one another — 

 approaching slightly to gamopetaly — than are the corresponding parts 

 of the flowers typical of the variety. The assumption of the existence 

 of three factors for size of corolla throws light on this phenomenon. 

 Lacking altogether one of the three factors for gigantism the variety 

 Mont Blanc Star cannot throw giants but if its constitution be AaBBcc 

 it may throw both AaBBcc and AABBcc forms, the former in larger 

 numbers than the latter. If the AABBcc form differs, as differ it must, 

 from the AaBBcc form it is described as a fluctuation. In other words 

 fluctuations or minor variations may owe their origin to the hetero- 

 zygousness (for one or more factors) of a factorial complex which is 

 completely lacking in one factor essential for the production of a given 

 Mendelian character. 



On the assumption that growth factors may condition cell chemistry 

 this hypothesis of the origin of fluctuations may be found to supply 

 the key to an explanation of the facts discovered by H. E. and 

 E. Frankland Armstrong (1912) with respect to the sporadic dis- 

 tribution of cyanophoric glucoside in herbage plants, such as Lotus 

 corniculatus. Their studies have brought to light the interesting fact 

 that the glucoside may be present in one plant or group of plants and 

 absent from another, and although it may be that climatic conditions 

 may play a part in the phenomenon it seems also probable that this 

 fluctuation is dependent on the genetic constitutions of the individual 

 plants. 



Again it will be at once evident that the cases enumerated in 

 Table IV, in which giants appear in Fi, are susceptible of explanation 

 on the hypothesis which has been put forward. 



Thus Crimson King (see Table IV) is itself a fairly massive plant 

 and may be supposed to contain two of the three growth factors. 

 Hence when crossed with a giant it gives an jPj which the expert 

 describes as semi-giant and an F2 (Table IV) composed of 18 giant : 5 

 non-giant. Thus : 



