'26 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



time becomes useless. The mycelium consists of more or less waved 

 articulated threads which give off here and there stouter erect threads, 

 with shorter joints, branched slightly above and producing at the tip of 

 each joint a large spore. The spores, or conidia, are at first oblong and 

 pale, showing one or two transverse septa. These rapidly acquire a dark 

 tint, elongate, become more or less linear, and consist of from seven to 

 eleven swollen divisions, of which the terminal one is mostly apiculate. 

 Each division contains a few minute oil granules (50-80 jx long). After 

 the spores have fallen they frequently split in the centre and give out a 

 globular body, which is in all probability reproductive. 



We strongly suspect that this fungus is not a true parasite, but made 

 its appearance subsequently, and was not the cause of disease. 



Gard. Chron. 1864, p. 938, fig. ; Cooke Hdbk. No. 1726. 



The "frosty mildew" caused by Cercosporella persicce has been 

 known in America since 1890 on Peach leaves. 



Peach Yellows. 



This is one of the most mysterious of plant diseases, and although it 

 has been known to occur in the United States for at least a century it 

 has not found its way into Europe. In recent years " thousands of young 

 and thrifty trees have been destroyed by it, and Peach growing has been 

 abandoned in several parts of the country where formerly there were large 

 and profitable orchards." The earliest symptom is the premature ripen- 

 ing of the fruit ; then diseased dwarfed growths appear on the trunks 

 and limbs. The limbs attacked are badly diseased the second year, the 

 entire growth being stunted and of a sickly green tinged with yellow. 

 After this they may languish for a few years, and then die gradually from 

 the extremities downwards. All efforts to discover fungoid mycelium has 

 failed, and it is only recently that the disease has been attributed to 

 microbes. In 1889 Professor Burrill intimated that he had found " in 

 th< tissues of the root and of the old and young stems of diseased trees 

 an organism classed with the bacteria which is not known to occur else- 

 where. This organism has been frequently obtained by method of 

 cultures under circumstances which preclude the possibility of its coming 

 from anything except the inner cells of the tree. He had it growing in 

 artificial media, and it exhibited all the peculiarities of a pathogenic 

 rather than a saprophytic microbe. He found it in every set of specimens 

 which he examined, known to be affected by the disease, and has 

 thoroughly tried in the same manner to find it in healthy stock and 

 failed." 



Silver Leaf. 



Stcrcum purjmreum (Fries). 



This disease has been known as affecting fruit trees in this country for 

 tally ;i quarter of a century, and has puzzled mycologists and pathologists 

 to account for the cause. Recently Professor Percival has conducted 

 ; onie experiments which he considers will demonstrate that the disease 



