226 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Stomata are present on bract-leaves, flower-stalk, calyx, and corolla. 

 A well-developed ovarian nectar gland is present. 

 Starch is present in great quantities in roots, stems, leaves, and 

 carpellary tissue. — M. C. C. 



Fungi attacking the Apple Fruits. 



1. Apple Scab. 2. Apple Rots in Illinois. By G. P. Clinton 



(U.S.A. Exp. Stn , Urbana, Bull. 67, Dec. 1901, and Bull. 69, February 

 1902). — In the first of these pamphlets the author describes the results 

 of botanical studies carried out during 1898, 1899, and 1900 on the 

 disease of Apples known as " Apple scab," caused by the parasitic fungus 

 Fusicladium dcndriticum. Goethe in 1887 suggested that this fungus 

 was a stage in the life-history of a fungus which had its later stage on 

 the dead leaves, and Aderhold in 1894 connected it with a species of 

 Venturia on the dead leaves. The investigation: of the author confirm 

 the view that Apple scab is merely a parasitic summer stage of a 

 permanent saprophytic fungus occurring on the fallen leaves. 



The Fusicladium stage occurs on the leaves and fruits, forming 

 distinct small circular olive patches, and in time causing puckering of 

 the leaves and sometimes death of the cells beneath. Young leaves 

 attacked often turn yellow and drop, but the leaves usually remain 

 attached to the tree until autumn. 



On the fruit roundish olive rough areas or "scabs" are produced, 

 sometimes spreading over a considerable surface. When very young fruit 

 is badly attacked, distortion and interference with normal development 

 occur, and sometimes the little fruits fall. 



The severity of the attack depends largely upon the weather conditions. 

 In years having wet springs, especially when damp cold weather prevails 

 during the opening of the leaf buds, the disease does most injury. 



Bordeaux mixture (4 lb. copper sulphate, 4 lb. fresh lime, 50 gallons 

 water) sprayed on the trees soon after the leaves begin to unfold, again 

 soon after the petals fall, and if the season has been favourable to the 

 development of the fungus about two weeks later, has been found an 

 effective means of preventing the disease. The second spraying may be 

 done with a mixture of Paris green and Bordeaux mixture if codlin moth 

 is troublesome (1 lb. of Paris green to 200 gallons Bordeaux mixture). 



The Fusicladium stage appears soon after the leaves begin to unfold, 

 and may be found until the leaves fall. It can more easily attack the 

 young leaves and fruits than older ones. It is more abundant on the 

 lower than on the upper surface of the leaves, and especially near the 

 midrib. It attacked the lower leaves more frequently than the upper. 

 On the leaves the mycelium grows between the epidermis and the cuticle, 

 and sometimes between the epidermal cells. It sends up conidiophores 

 which penetrate the cuticle, and from which lanceolate, acute, reddish 

 olive-coloured spores are successively abstricted. Sooner or later the 

 complete collapse of the epidermal cells is caused. In the fruit the 

 mycelium often forms a pseudo- tissue several cells deep before the spores 

 are produced. 



The fungus was in only one case found on twigs, and that on a tree 

 very badly infected, but all trace had disappeared before the spring. 



