280 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



plants inoculated and kept at ordinary room temperatures become 

 infected (p. 149). 



Light is of marked indirect importance in many cases, though it 

 is considered doubtful if it has any direct effect upon the parasite 

 (p. 150). Celery is damaged seriously by the early blight fungus 

 when grown in strong sunlight, the disease appearing to develop best 

 during bright hot days with dewy nights, but it is controlled to a 

 considerable extent by partial shade. Most fungus diseases^ how- 

 ever, develop best in shady conditions, especially the powdery mildews. 

 Experiments with etiolated plants show opposite results. Petunias 

 and lettuce in this condition were attacked by the hemi-parasitic 

 fungus Botrytis, though the normal green leaves of these plants are 

 not infected by it. On the other hand the rust which infects brome 

 grasses could not do so when the grasses had become etiolated (p. 151). 



A. P. 



Diseases, Two Dangerous Imported. By P. Spaulding and Ethel 

 Field (U.S.A. Dep. Agr., Farmers' Bull. 489). — The two disease 

 fungi concerned are Peridermium Strobi and Chrysophlyctis endo- 

 biotica. The latter, so far, has not found its way into the United 

 States, although it is known in Newfoundland. 



Peridermium Strobi, or white pine blister rust, has its aecidial stage 

 on the leaves of currants and gooseberries, and spreads from there on 

 to the bark of Pinus Strobus and many other five-leaved pines. The 

 stage on the pine is the more destructive of the two, and has caused 

 so much damage to nursery stock, &c, that the use of the white pine 

 has been discontinued in Denmark, and Holland and is largely given 

 up in England. 



The other disease, Chrysophlyctis endobiotica, or warty disease of 

 potato, gains entrance into the tubers through the tender tissue at the 

 eyes. In mild attacks the eyes first appear greyish, then brown, and 

 finally turn black. In more advanced stages one or more nodules 

 appear, varying in size from a pea to wrinkled coral-like lumps as large 

 as or larger than the tubers themselves. The potatos are finally 

 reduced to a black, pulpy, evil-smelling mass. The nodules are white 

 when young, but turn black later. The organism develops in the 

 tissues, forming summer thin-walled sporangia in the cells. These 

 sporangia burst and liberate spores which infect other tubers. The 

 winter sporangia are developed in the same way, but are thick-walled, 

 and live through the winter either in the soil or in diseased tubers. In 

 spring these sporangia ripen and liberate numerous motile spores. 



The winter sporangia can remain viable for eight years, so that 

 land, when once infected, should not be cropped with potatos for eight 

 years or longer. 



No remedies, so far, have proved effectual. Only clean seed from 

 non-infected land should be planted, and great care should be taken 

 not to feed diseased tubers, unless previously boiled, to stock, as the 

 spores can pass through an animal unharmed, and infection has been 



