xxv.] CORN MILDEW AND BARBERRY BLIGHT. 185 



showed the least sign of germination, but all had perished. 

 These facts, of course, do not prove that the mycelium is 

 perennial, but we think it proves that the spawn can reacli 

 the embryo of seeds, and in bad cases kill them. We also 

 think it suggests the possibility of seeds less badly diseased 

 being able to give rise to diseased seedlings, exactly as in the 

 case of the Dianthus seeds, which showed the Puccinia in 

 the seed-leaves. In the Proceedings of the Royal Society, 

 No. 228, 1883, Mr. Plowright has illustrated the ^Ecidio- 

 spores belonging to Mahonia Aquifolium, Lind., germinating 

 upon the epidermis of a fragment of wheat-leaf. Six 

 spores are shown : five are germinating three germinal 

 threads are entering the stomata; but no less than seventeen 

 little branches of the mycelium are shown naturally and 

 correctly running along the little furrows belonging to 

 the junctions of the cells which form the leaf cuticle. 

 The illustration simply proves that the germ-tubes will 

 run anywhere where there is a depression, or run into 

 any little orifice. After eleven days, not five or six as 

 with Bonninghausen, Uredo appeared upon the plants 

 experimented upon. 



Many cases are well known where host plants are always 

 so saturated with parasitic disease that it is almost impos- 

 sible to find the host without the parasite. Pythium 

 equiseti, Sdbk., is so common on Equisetum that we have 

 seldom found an Equisetum without it. Cress seedlings 

 are plagued in a similar fashion with another Pythium. 

 Now, who would place any reliance on experiments made 

 with a view to inoculate Equisetum and cress with Pythium, 

 when it is well-known beforehand that every plant is 

 probably already permeated with the virus of the parasite 

 in a latent state ? 



Personally we do not esteem the fact of spores germi- 

 nating on the cuticle of a leaf as of the slightest value. 

 Nearly all spores will germinate in warm moist air upon 

 any surface, and the spawn-threads will run into any slight 

 depression, or any orifice, provided it is large enough. 



