388 Lecture on the Parasitic Fungi of the British Farm. 



}\ower. This uredo confines its attacks chiefly to the seed of 

 wheat amongst our cereals, but some other plants, as the convol- 

 vulus, and of" the grasses, rye-grass, hromus, and j9oa, are subject 

 to have their seeds destroyed in a similar maimer. 



(5.) The^euredines, as well as mildeic, ihou^h. till recently not 

 understood, have lono- been the subjects of observation. Moses 

 threatened the disobedient Israelites with mildew, and the Romans 

 had their false god Rohigo, whom they thought to propitiate for 

 the preservation of their fields from the disastrous attacks of these 

 diseases. A feast called Robigalia, to this deity, was always kept 

 on the 25th of April, to deprecate blasting and mildew. The 

 diseases themselves were long matters of curious speculation, and 

 they were, till lately, regarded as accidents of vegetation resulting 

 in a mass of injured cells from the dampness of the soil, excess of 

 manure, or fogs^ or punctures of insects, and have even been 

 attributed to the presence of the berberry, a fungus of which, 

 called a'cidiuin, is shown in Fig. JO. On the left is seen a piece 



Fig. 10, CEcidium of tlie Berberry. 



of the leaf of the berberry with the spots of cecidium upon it. 

 On the right, one of these receptacles, containing spores, is 

 magnified to show the form of this fungus. The mycelium on 

 which it grows is also visible. There have been many botanists 

 who have believed that the spores of oscidium come up 3.%uredines 

 when they fix upon any cereal. It is the microscope which has 

 enabled us to recognise in all these parasites a true fungal cha- 

 racter, and to trace their growth ; but the damage accruing from 

 them has not been adequately estimated, for they never appear in 

 the farm or garden without injury to the produce. For example, 

 {e\N can have failed to notice the effects of uredo on the rose-trees, 

 and also, but less frequently, on geraniums. 



(6.) Numerous have been the speculations, and often inge- 

 nious the experiments, on the way in which the reproductive 

 sporules find entrance into corn-plants. Various remedies have 

 been tried, and some with success, as in the case of hunt, or 

 pepper brand, which may be effectually checked by good dressing 

 of the seed. The principle of the dressing is the conversion oi 



