11 



"REVERSION" AND RESISTANCE TO "BIG BUD" 

 IN BLACK CURRANTS. 



By a. H. lees, M.A. 



{Plant Pathologisf, Agricultural and Horticultural Research Station, 

 Long Aslifon, Bristol.) 



(With Plates III— VI.) 



In this paper owing to the apparently close connection between Rever- 

 sion and Big Bud it is proposed to treat the two subjects together. It 

 seems impossible to explain Reversion without discussing Big Bud and 

 special cases of the latter necessitate for their explanation and therefore 

 for the explanation of certain cases of Reversion, reference to the factors 

 governing resistance to Mite attack. 



For these reasons it has been necessary to combine in one paper 

 material that would otherwise have been better suited for two. 



REVERSION. 



This disease is known under various names, such as "Going wild," 

 "Running off," "Nettle leaf" and possibly others. "Reversion" seems 

 now to be the commonly accepted name and, being so, is used here. 

 The name of course implies that the plant is reverting to the wild type. 

 Scientifically the idea is extremely improbable and there is nothing to 

 show from the observed facts that such a process has been or is going on. 

 For lack of a better name however the term reversion will be used in this 

 paper. 



Chaeacteristics of the Disease. 



In a fully reverted bush the following points may be observed. 



(1) The fruit "runs off" ; that is, at picking time either no berries are 

 found on the strig or only a very few generally undersized fruits instead 

 of the many plump ones of the normal bush. These few berries may be 

 at the base or at the tip of the strig. 



(2) There is an extensive growth of the laterals resulting in a crowded, 

 instead of an open, form of bush. 



(3) The internodes are abnormally long and thin. 



