182 DISEASES OF FIELD & GARDEN CROPS. [OH. 



haps impossible ; and there is no proof that anything of 

 the sort has ever occurred. 



We have little doubt that the mycelium of both the 

 mildew fungi and the spawn of both the ^cidia are peren- 

 nial, and that both can live on from year to year for an 

 indefinite period without aid from each other. Mr. Berke- 

 ley, in vol. i. of the Journal of the Royal Horticultural Society, 

 writes at p. 25 : " The mycelium of cereal fungi is known 

 to exist from the earliest period in corn ;" and further on 

 he remarks that " a diseased stock can scarcely be expected 

 to produce a perfectly healthy offspring," and " it is cer- 

 tain that the germs of cryptogamic plants may be present 

 in tissues, and yet remain more or less inert." Referring 

 to dEcidium, he says, in reference to the parasite of the 

 anemone (Introduction to Cryptogamic Botany, p. 323), " the 

 leaves, which will be eventually covered with the fungus, 

 show that they are impregnated with its mycelium as 

 soon as they make their appearance." If these facts are 

 admitted, and ^cidium quadrifidum, D.C., of the anemone 

 is acknowledged to be perennial, another point arises. How 

 can any observer tell that the plants he is experimenting 

 with have not the germs of disease already in their tissues ? 

 We, as well as many other observers, have shown that seeds 

 apparently sound will often, on germination, show disease 

 in their seed leaves ; such plants are saturated with the 

 germs of disease from their earliest period of growth. 



An instance was adverted to by us in the Gardeners' 

 Chronicle for 26th January 1884, p. 120, where a well- 

 known nurseryman in a large way of business had im- 

 ported Dianthus seeds direct from Japan. These seeds 

 were carefully grown under glass, and, immediately they 

 were up in the seed-pans, they were all attacked and 

 destroyed by Puccinia lychnidearum, Link. On making a 

 microscopical examination of a series of these seeds we 

 detected mycelium inside the integument which surrounds 

 the embryo or infant plant and within the coat of the seed. 



Dr. M. 0. Cooke has published a case where seeds 



