340 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Poinsettia, A double (P. pulcherrima plenissima). By Ed. Andre 

 (Bev. Hort. March 1, 1905, p. 109, and June 16, pp. 294-296 ; coloured 

 plate). — A splendid form with numerous large bracts of intense scarlet 

 colour. A similar form appeared in England about thirty years ago, but 

 is apparently lost to cultivators. This, therefore, is a fresh sport 

 introduced by M. Demole, Cannes. The history of both introductions is 

 given.— C. T. D. 



Potato Diseases and their Treatment. By B. T. Galloway 

 (U.S.A. Dep. Agr. Farmers 1 Bull. No. 91, 1899 ; with 4 cuts). — A popular 

 summary of the chief diseases to which potatoes are liable, with the 

 most approved remedies. Issued by the Department for the information 

 and assistance of farmers and other potato-growers in the States, but 

 containing nothing novel to call for remark. — M. C. C. 



Potatoes, Disease-resistance in. By L. E. Jones (U.S.A. Dep. 

 Agr. Bull. 87, Dec. 5, 1905). — The aim of this bulletin is to present in 

 concise form what is known about disease-resistance in potatoes. Certain 

 minor diseases of obscure nature are first considered. Scab diseases' are 

 in most cases parasitic, but the severity is less in Europe than in America. 

 Of stem diseases the commonest is * blackleg,' which is a bacterial disease. 

 ' Factor ' and ' Up to Date ' showed a considerable degree of resistance in 

 England. ' La Czarine ' and other varieties are reported to show resistance 

 to a bacterial stem disease in France. 



Disease-resistance in potatoes to Phytophthora is relative, not absolute ; 

 no variety known being wholly proof against late blight and rot. It 

 seems related to general vegetative vigour, and is therefore in a measure 

 dependent upon cultural and developmental conditions, and tends to 

 decrease with the age of the variety. It can be restored by originating 

 new varieties from seed, especially of hybrid origin. Not all seedlings 

 show superior disease- resistance. 



The use of other species of tuber-bearing solanums for hybridising 

 offers some promise, but no practical results have yet been secured. 



Possibly the disease-resistance in established varieties can be improved 

 by selection, but this has not been proved. Early varieties may escape 

 disease by maturing before it becomes epidemic, but when similarly 

 exposed are less resistant than late varieties. 



The source of seed tubers is a matter of importance, northern-grown 

 seed giving plants of superior disease-resistance in Europe ; seed from 

 a crop that was not too highly fertilised is probably preferable. Possibly 

 tubers are better for seed purposes if dug before they reach full maturity. 



High fertilisation, especially nitrogenous, lowers the power of the plant 

 to resist both blight and rot. 



Varieties relatively rich in starch are more resistant to rot ; those richer 

 in protein are more susceptible to it. 



So far as skin characters are an index, the red varieties with thick and 

 rough, skin seem more resistant, as a class, than the thin-skinned white 

 varieties. 



So far as stem and foliage characters are concerned, the evidence 



