GIGANTISM IN PRIMULA SINENSIS. 



By FREDERICK KEEBLE, Sc.D., 

 Professor of Botany in University College, Reading. 



CONTENTS. 



SECTION '*<*■ 



I. Introdaction 163 



n. Gigantism in Primula tinensis 164 



TTT . The Mode of Origin of Giant White Queen Star 165 



rV. A Histological Comparison of Giant with Normal White Qneen Star. 168 



V. The Genetical Behaviour of Giant White Queen Star: with Notes on 



the Genetics of Gigantism in P. sinensis 172 



VI. Theoretical Considerations 185 



Vn. Summary 186 



L Introduction. 



Many of our cultivated plants are to be met with in giant and 

 dwarf, as well as in normal forms, and anyone who will consult the 

 pages of nurserymen's catalogues may learn that the plant breeder 

 has exercised his genius no less successfully in moulding the form of 

 plants than in modifying the colours of their flowers. The universality 

 of the phenomenon of gigantism justifies the belief that a comparative 

 study of the physiology of giant and normal plants will lead to results 

 of interest and value. But such a comparison must be accompanied 

 by a study of the genetical relations which exist between giant and 

 normal forms ; for although, so far, only one type of giant has been 

 observed among plants, analogy with animals would suggest the possi- 

 bility of the occurrence of more than one type of gigantism in the 

 vegetable kingdom. {Cf. Gilford, 1911.) 



The plants in which the phenomenon of gigantism has been investi- 

 gated include Oenothera gigas (de Vries 1901, Gates 1909), Lathyrus 

 odoratus (Bateson 1909 a) and Pisum sativum (Mendel, see Bateson 

 1909 B and Keeble and Pellew 1910). In all these cases the giant is 



