12 



On the Diseases of W heat. 



divided into two chambers, each filled with spornles. Thej taper 

 gradually at the base into a fine stalk. The sori (or patches of 

 spores) are composed of multitudes of these bodies, which some- 

 times burst through the epidermis of the stem and leaves, in such 

 profusion, that the whole plant appears as if it had been scorched. 

 I have observed this fungus intermixed with the rust-fungi in a 

 way which strengthens my opinion that they are identical ; but I do 

 not wish to discuss this point any further, as my observations on 

 mildew have hitherto been very slight. The only example which 

 this year came under my notice, occurred in two fields at Audley- 

 end, in one of which Lord Braybrooke informs me, " that wheat 

 was never grown before, the ground having been sheep-walk and 

 absolutely worthless, until it was ploughed up some years ago, 

 and since been farmed on the four-course system. The ground 

 being much exposed, and with a northern aspect, the ploughmen 

 call it Freeze-land. The seed was supposed to be pure Talavera." 

 The seed in the other field was Hickland's-prolific. As these 

 fields were mildewed in a season remarkably free from this blight, 

 these circumstances are worth recording — and in addition I may 

 observe, that the soil was poor chalk-land, and the field of Tala- 

 vera surrounded on all sides by high hedges and plantations. The 

 mildew in the other field was confined to one corneT. 



Section VII. — On the precautions to be taken against Rust 

 and Mildew. 



I have very little that is satisfactory to report on this head. I 

 do not think it has been clearly determined by experiment, 

 whether the sporules of the rust and mildew fungi are absorbed 

 by the roots of corn, like those of the bunt and smut fungi ; or 

 whether, (which seems to be the more prevalent idea) they enter 

 through those minute pores on the stem and leaves which bota- 

 nists term " stomata."" The fungi at first make their appearance 

 in little cavities seated immediately beneath these pores, which 

 certainly looks very much as if the sporules entered there. The 

 stomata are naturally exhaling organs, continually discharging, 

 under the influence of light, a large proportion of the water im- 

 bibed by the root. But in moist weather, this function is im- 

 peded, if, in some cases, it be not actually reversed ; when it 

 would be easy for the sporules to enter these invisible stomata, 

 with the moisture imbibed by them. The fact, however, stands 

 in need of proof ; and hitherto the evidence is more in favour Of 

 similar fungi being imbibed by the roots of the plants which they 

 attack. Mr. Knight indeed, w^ho is high authority, particularly 

 insists upon mildew being induced by foggy weather, happening 

 at a time when the ground is particularly dry : circumstances 

 which we may readily understand as likely to convert the stomata 



