On the Diseases of Wheat. 



11 



curved bodies arising from the receptacle of the Uredo, and con- 

 taining globular orange bodies exactly like that of Uredo ; but 

 I am not at present prepared to assert that Aregma is only an 

 altered form of Uredo." Perhaps I have said too much on this 

 purely botanical question ; but an independent testimony in mi- 

 croscopic observations is often of value ; and repeated observations 

 have fully satisfied me of the truth of what I have advanced. 



It will now rest with agriculturists to observe whether mildew is 

 not always preceded or accompanied by rust — and botanists must 

 determine the manner in which the three forms of spores developed 

 in these diseases are related ; if indeed they really belong to the 

 same fungus. My conjecture is — that whilst one of the uredines 

 (U. rubigo') is a particular form of spore^, which does not undergo 

 any further change, the other ( U. linearis) is the young state of a 

 distinct form of spore which^ when further advanced, is called 

 Puccinia graminis. I may add, that in order to be quite positive 

 that I had found the U. linearis, 1 sent Mr. Berkeley a specimen 

 of the straw to ascertain his opinion w^hether I was correct in sup- 

 posing that the three fungi were co -existing in the same plant. 

 He replied^ I perceive in your culm, Puccinia graminis inter- 

 mixed with Uredo linearis, and a few bad specimens perhaps of 

 Uredo rubigo vera."" With Mr. Berkeley's opinion against me, 

 I offer my conjecture to future observers with the greatest hesi- 

 tation. 



Section VI. — On the Mildeio (Puccinia graminis). 



If agriculturists appear to have confounded under the name of 

 rust, the attacks of fungi which botanists consider to belong to two 

 distinct species ; so also have they frequently applied the name of 

 rust as well as mildew to the disease we are about to notice. It 

 will be seen by what I have stated in the last section that I am 

 inclined to consider these two diseases to be mere modificatians in 

 the attack of the same species of fungus, but that further obser- 

 vations are required to settle this question. For the present, then, 

 we must consider the mildew-fungus not merely as a distinct 

 species, but also as belonging to a different genus from the two 

 rust-fungi. The form of its spores is indeed very different from 

 those we have already noticed. Mr. Bauer long ago published 

 figures in which all the forms of the mildew- fungus are accurately 

 delineated. This plate accompanies a short account of mildew by 

 the late Sir Joseph Banks, which was published as a separate 

 pamphlet, but afterw^ards reprinted in the second volume of the 

 " Annals of Botany ;" again, in " Curtis' s Account of Grasses ;" 

 and again, but without Mr. Bauer's figures, in the sixth volume of 

 " the Pamphleteer." The ripe spores of this fungus are little 

 intensely dark -brown club-shaped bodies, having the thicker end 



