294 Practical Hints [ch. 



between a white and a coloured P^'imtda Sinensis is figured 

 in Plate VI. The results of this mating have for several 

 years been studied by Mr R. P. Gregory in collaboration 

 with me. Though the quantitative relations between the 

 types, and their factorial composition are still not completely 

 worked out, the case forms a good illustrative example of 

 the operation of Mendelian processes. The coloured parent 

 is Sutton's Crimson King, a well-known very dark red sort, 

 with red stigma, red spots round the eye and full red stalks. 

 The white parent used was Primrose Queen, a stellate or 

 Star Primula, with a white flower and reddish stem. This 

 white type has the large yellow eye spoken of in connection 

 with the inheritance of heterostylism (p. 70), and as there 

 described, the style does not reach above the level of the 

 anthers, this being the condition known as homostyle. 

 Both types breed absolutely true to their respective 

 characters. 



The plants, F^, produced by crossing these tw^o types 

 are quite uniform. In habit they are intermediate betw^een 

 the star type and the compacter shape of Crimson King. 

 The flow^er shape is also intermediate. The petals are 

 whitish, with a slight tinge of magenta, especially on the 

 lateral edges. When kept warm they lose the colour 

 almost entirely, but when they are kept cool, the colour 

 increases somewhat in amount. 



By the self-fertilisation of such F^ plants a very complex 

 F^ series is produced. Plate VI gives a fair idea of some 

 of the more conspicuous types which appear, though it will 

 be understood that only the colour and the shapes of the 

 individual flowers can be represented there. In the mode 

 of growth, the shapes of the inflorescence and many other 

 features there is an equal diversity, so that an observer not 

 accustomed to the results of crossing may well find it 

 difficult to believe that this heterogeneous assemblage of 

 plants can all be the offspring of a single individual. A 

 systematist might make ten or even twenty species out of 

 such a family, w^ere the several types found isolated in 

 nature, and no one could accuse him of excessive ''splitting." 



The magenta colours are evidently due to a factor 

 epistatic to the crimson or claret-coloured reds, and this 

 factor was obviously introduced by the white parent. In 



