EXPERIMENT STATION BULLETINS. 



327 



Fig 3. 



Fig. 4. 



Fig. 3. Section through a scab spot, a, spore (conidium); b, hypha or supporting thread; c mycelium, 

 or plant body of fungus- d, epidermis of apple ; e, cells of apple. Fig. 4. /, spores greatly magnified ; 

 g, h, spores germinating. 



porting threads; these are, as a rule, one-celled, but occasionally they are 

 divided near the middle by a transverse partition. The pear-shape bodies 

 (Fig. 4) are the spores of the fungus, and it is through their agency that 

 the parasite is propagated. The brownish threads serve merely as supports 

 for the spores, while the dark mass of tissue constitutes the body of the 

 fungus, or, if I may so express it, its roots, branches, and leaves. When 

 full grown the spores separate readily from their supporting stalks, and 

 being exceedingly small and light are easily wafted from place to place by 

 currents of air. In this way they reach healthy fruit and leaves, and, if 

 the proper conditions of moisture and heat are present, they quickly ger- 

 minate by sending out slender tubes, which bore their way into the leaves 

 or fruit, and ultimately give rise, just beneath the cuticle or skin, to dark 

 masses of cells like those already described. At first, this mass of fungous 

 tissue is entirely beneath the cuticle, but, as the former continues to grow, 

 the latter is ruptured, and it is then that another crop of stalks and spores 

 is formed. In this way the fungus continues its development throughout 

 the growing season, the crop of spores formed in the autumn living over 

 winter on the old leaves, fruit, and young branches." 



Another quite distinct disease, the nature of which has not been dis- 

 covered, frequently attacks the leaves, and causes them to rapidly turn 

 yellow, or brown, and drop off. Although it has no resemblance to apple 

 scab, it is frequently mistaken for it. Not only is scab injurious to the 

 tree, by reducing the leaf surface, and its power of assimilating food, but 

 the fruits are reduced in size by the scab spots that form on them, they are 

 rough and misshapen, and often, in case of certain varieties, become 

 utterly worthless for packing. 



Careful experiments, here and elsewhere, for the last three years, have 

 shown that, even with varieties most subject to attack, a difference of from 

 50 to 75 per cent, can be made in the number of scabby fruits by proper 

 application of fungicides, at an expense for labor and materials of from 10 

 to 15 cents for the largest trees. The treatment is exactly the same as is 

 recommended for the grape diseases; but, if the season is not too wet, three 

 applications will suffice. 



