152 MASSACHUSETTS HORTICULTURAL SOCIETY. 



right time, and after overcoming his advances we maj? expect 

 to gather a harvest of beautiful flowers. Later on, the rose-bug 

 will be the next invader, and must be picked off as soon as he 

 appears. Last season there were but few with us. The green fly 

 must also be looked for, and hellebore is useless for it, whale-oil 

 soap and tobacco steeped together being the only remedy. 



We now come to one of the worst drawbacks to satisfactor}'^ 

 rose culture, viz : Mildew, a peculiar disease caused by a fungus, 

 Sphcerotheca pannosa, which, if neglected for a single day, 

 increases with wonderful rapidity. If the mildewed leaf of a rose 

 is put under a microscope, it will, says Mr. Worthington G. Smith, 

 be seen to be covered by thousands of threads of mildew, each of 

 which consists of eight or nine spores, which as they ripen are 

 carried off by the wind. The spawn threads are here and there 

 dotted over with little black grains, each grain so small as to be 

 invisible without a common magnifying glass. Under a strong 

 hand lens, the dots look like minute but perfectlj' round grains of 

 gunpowder. Each dot is seen as a round black box with a num- 

 ber of curious, brown, sinuous, radiating appendages. Each 

 globular box is no larger than the point of a needle. There is a 

 comparatively thick outer coat to this box, made up of minute 

 pieces, spliced or dove-tailed together like the shell of a tortoise. 



One infected rose leaf will in the autumn bear hundreds of these 

 black boxes, each with its contained air-tight bladder of eight 

 living spores ; the precious boxes are quite impervious to drought, 

 frost, or water. 



Another of the worst diseases of the rose, is the Orange Fungus, 

 Coleosporium pingue, which in its earlier stages is pale yellow, 

 then becomes orange, vermilion, brown, and at length black.* 



Mildew does not seem seriously to affect the life or strength of 

 the plant, as^ being a surface disease it does not strike to its 

 marrow. For instance, the rose Comtesse de Serenye is one of the 

 worst for mildew I have ever known, and yet it is a rose that 

 grows with great vigor from year to year. In fact, mildew does 

 not claim as its victims the weakest growers, but takes the 



*The Rose Mildew is described and figured in the Journal of Horticulture and 

 Cottage Gardener, Vol. 72, pages 478,479; in the Rosarian's Year Book for 1886, pp. 

 4-14, and in Paul's Rose Garden, 9th edition, pp. 14G-148. The Orange Fungus is de- 

 scribed and figured in the Gardeners' Chronicle, Vol. 26, New Series, pages 76, 77; in 

 the Rosarian's Year Book for 1887, pp. 4-13, and in Paul's Rose Garden, pp. 151, 152. 



