STUDIES IN VARlPXiATlON. I. 



U\ W. HATKSON. M.A., KH.S. 



(With Platos III and IV aixl One Tcxt-fi^Miic.) 



Thk phononuMia of variegation dnc to absence or deficiency ot 

 chlorophyll have for some time been a special object of study at the 

 John Innes Horticultural Institution. The inter<'st of the subject lies 

 in the circumstjinee that in variegated plants an opjx)rtunity is given (»f 

 witnessing somatic distribution «»f a character, deficiency of chlorophyll. 

 alrciidy known to be in many plants a Mendelian recessive. It is true 

 that up to the present time no direct experimental evidenc** exists sufti- 

 cient to prove that the chanicters, presence and absence of chlorophyll, 

 heterozygously combined together in fertilisation, am actually lead to 

 the production of a variegated zygote; but from the general coui-se of the 

 phenomena of mosiiicism, presenting not very rarely. two allelomorphic 

 differences in juxtiiposition in the same plant, we may assume without 

 much reservation that this interpretation is admissible. Baur', indeed, 

 speaking of a blue Veronica bearing a white-Howered branch, observed 

 by de Vries, is disjx>sed to refer such ca.ses to original mutation by 

 loss, r;\ther than to somatic segregation of charactei-s in heterozygous 

 combination. Evidently there is at present no means of positively 

 distinguishing the two possibilities, but I incline to regard .somatic or 

 vegetative segregation as on the whole the more acceptable account. 

 If this hypothesis be the true one, we have in variegation a visible 

 model or plan of segregation by which the properties of the germ-cells 

 are certainly determined in many instances, and we may at least enter- 

 tain the possibility that in plants segregation in properties not thus 

 producing visible .somatic effects may also be similarly determined. 

 The series of examples which will be descril)ed in the present and 

 succeeding papers illusti-at** mi.scellaneous features in this special kind 

 of segregation. Apart from any question of wider application \\\v 

 phenomena are, 1 think, of obvious genetic im[>ortance. 



' y. /»//■/ /»MH.7, Ac. p. 218, Note. 



