24 Structitral Characters: Plants [CH. 



1 6. Palmatifid or ' 'palm-leaf" and pinnatifid or 

 " fern-leaf." Primula Sinensis (Fig. 7). 



The fern-leaved form arose in English horticulture about 

 1860 as a variation from the normal type. I have had 

 opportunities of seeing its genetic behaviour on a large 

 scale at Messrs Button's, and many experiments have been 

 made with it by Mr R. P. Gregory in conjunction with me. 

 Dominance is usually complete, but at Messrs Button's I 

 have seen on two occasions strains containing plants of 

 intermediate leaf-shape, which were presumably hetero- 

 zygous, for the two types occurred on sister-plants. The 

 leaf- shape is entirely independent of the colours and other 

 features of the plant, and can be transferred bodily from 

 one colour-type to another. Messrs Button's varieties 

 " Mont Blanc" and "Sirdar," for example, are sold both in 

 the palm-leaved and in the fern-leaved forms. 



Fern-leaf (R) Palm-leaf (>) 



Fig. 7. The two types of leaf found in Primula Sinensis. 



17. Leaves and petals normal or laciniated. Cheli- 

 donium majus. de Vries (290) and (298), i. p. 134. 



This case is interesting in comparison with No. 15. In the Nettle, 

 serration is a dominant, while here laciniation is a recessive. A careful 

 study of the physiological distinction between the two processes would 

 probably lead to important results (cp. Leake, 170, on leaves of Cotton). 



