204 3Iississippi Valley Horticultural Society. 



shaped, i. e., thicker towards the apex, and consist of a single cell, or have a 

 transverse partition making two cells. 



In the early condition of the allected spot, the mycelium and spores oc- 

 cupy a small central area ; but as growth continues the mycelium gradually 

 spreads into the surrounding tissues, and soon dies in the centier, so that the 

 fungus is found in a ring at the outer edge of the affected spot. Sometimes 

 this spreading continues for months from the same initial point, and a large 

 part of the surface of a fruit may be involved, or, for some reason, the fungus 

 soon perishes, and the spot remains small. Frequently, numerous small 

 spots near together coallesce, and thus, in another Avay, cover the surface. 



Spores are produced by the fungus in a similar manner when it inhabits 

 the leaves and young stems, only they are never found in such luxuriance of 

 number, on account, no doubt, of the less available nutriment. There seems 

 to be no special season for their maturity — they form and ripen throughout 

 June, July, August, and SejDtember, and as soon as mature, germinate when- 

 ever suitable conditions of moisture, etc., are present. If in this condition 

 the spores reach the living surfaces of the leaves, twigs, or fruit, the filament 

 produced by the germinating tube, penetrates the tissues and a new crop of 

 mycelium and spores results, together witli the injured condition of the host. 



There are those who, admitting the presence of the fuAgus in this destruc- 

 tive disease, deny its agency as the cause of the difficulty. With them it is a 

 secondary result, a mere accompaniment or follower of the real destroyer. 

 In the majority of such cases we are asked to seek for the latter in the con- 

 ditions of the climate or the inherent peculiarities of the affected plants, It 

 is true the exact connections and the special processes by which heat or cold? 

 wet or dry, starvation, over-cropping, etc., produces the effects just as they 

 are observed in time and space are never explained by anyone who pretends 

 to be informed upon the subjects of vegetable physiology and pathology ; but 

 talk is cheap, and never easier than in general speculations by those who do 

 not care to be exact and definite, and especially by those who do not look 

 close enough to see the obstacles in the way. It is often easier to get a full 

 account of what exists in the center of the earth than what there may be 

 behind a picture hanging upon the wall of a room occupied by the inform- 

 ant. In the former case he does not feel restrained by the possibilities of 

 proof, and does feel that his notion is as good, at least, as that of his auditor 

 can be. The two may disagree, but that does not hurt anything. 



So, in these apparently difficult problems of disease in plants, it not unfre- 

 ijuently happens that opinions are the more tenaciously held the less the real 

 knowledge possessed upon the subject. When the bark of an apple tree is 

 found after a snow-storm to be freshly gnawed, and when the well-known 

 track of a rabbit is seen about it, no one thinks of saying, " I admit the pres- 

 ence of the rabbit and the quality of its teeth for this work, but contend that 

 we should not account it the cause of this wound. If the snow had not fallen 

 the animal would not have touched the tree, hence the snow is the real 

 gnawer of this bark.' Or, "if the bark had not been palatable and nutri- 



