105 



proves to consist of a tangled mass of olive-coloured inj^celium, which 

 pfives origin to numerous clusters of various sizes, composed of verj- 

 large, globose cells, each having two septa crossing at right angles. 

 This condition of the fungus under consideration was at one time 

 considered as an entity, and was known as Coniothecium chomatos- 

 poTum, Corda. During the autumn and winter the dark-coloured 

 mycelium, emerging through the ruptured blisters, spreads on the 

 surface of the shoot, forming blackish-olive patches of varying extent. 

 The mycelium of the fungus is confined to the cortex, which is killed 

 down to the wood, and during the winter the bi-anch dies. la the 

 •spring the masses of large cells of the Coniothecinm give origin to 



1 





^^ — ' 1 J m. J 



myriads of small, elliptical, hj^aline spores by a process of budding, 

 and these minute spores are capable of infecting young apple shoot?, 

 and giving origin to the Coniothecvum condition of the fungus, which 



thus capable of reproducing itself indefinitely without the inter- 

 vention of the two other stages of the fungus to be described, known 

 respectively^ as Fhoma mali^ Schulz and Sacc, and Diaporthe amhigua, 

 Nits., the latter being: the asci^ferous form. The Vlioma and the 

 Diaporihe are boil] pure saprophytes, appearing on the branchea 

 killed by the Coniotltecium., which is the only parasitic form included 

 in the life-cj'cle of the fungus. 



The small, hyaline spores produced by budding from the large 

 Coniothecium cells were placed on sterilised and uninjured young 

 apple shoots, protected from outside infection by waterproof paper. 

 After an interval of seven weeks, small blisters were present on the 

 shoot, which, on microscopic examination, proved to be caused by 

 the growth of masses or conglomerations of large Coniothecium cells. 

 These masses continue to increase in size and press the epidermis 

 upwards, at first forming a w^art or blister; eventually the epidermis 

 is ruptured. The blisters invariably first appeared close to_ the 

 lenticel, which suggests that infection only occurs at these points, 

 and that the budding spores cannot enter through the unbroken 

 epidermis. In course of time, the mycelium spreads in the cortex, and 

 blisters, due to clusters of cells, may appear at any point on the shoot. 

 When budding spores are sown in a nutritiv^e medium, the mycelium is 

 at first colourless and very slender, and gradually passes through a pale 

 olive to an almost opacpie blackish-olive colour, and at the expii'-'^- 

 tion of about six weeks, numerous conglomerations of large cells are 

 present. The large cells commence budding at once. When petri- 

 dish cultures of budding spores are about three months old, the 

 -t^homa stage of the fungus is produced in abundance. Fhoma spores 

 from such cultures, sown in a nutrient medium, gave origin, first to 

 the Coniothecium condition and afterwards to the Fhoma. Phoma 

 spores from the same soui-ce, when placed on young apple shoots, 

 gave origin to the Coniothecium condition of the fungus. In every 

 experiment with Fhoma spores, whether obtained from pure cultures 

 or from the Fhoma on shoots tliat had been killed the previous year 

 h' the Co7iiothedum, the first product of germination was the Cmm- 

 thecium condition, followed by the Fhoma ; hence it may be^concluded 

 tliat the infection of young shoots and fruit may also be due to the 

 Fhoma stage of the fungus present on dead shoots. 



Wlien the fruit is attacked, the effect produced depends to a great 

 extent on the aoe at which infection occurs. On the young, hard fruit 



