Peach scab and its control . unusual, however, forthe first division to be transverse, the daughter cells dividing tangen-tially. The two or three activelyconcerned hypodermal layers are,in each case, rapidly convertedinto a fairly uniform barrier ofthin corky cells of meager proto-plasmic content. As the lesionsage and the epidermal cells be-come more and more outer layers of subepidermalcells die and turn brown. After the advent of the dormantperiod of the host, the fungus con-tinues to develop throughout thefall, mild periods of the winter, andthe spring. The subcuticular h
Peach scab and its control . unusual, however, forthe first division to be transverse, the daughter cells dividing tangen-tially. The two or three activelyconcerned hypodermal layers are,in each case, rapidly convertedinto a fairly uniform barrier ofthin corky cells of meager proto-plasmic content. As the lesionsage and the epidermal cells be-come more and more outer layers of subepidermalcells die and turn brown. After the advent of the dormantperiod of the host, the fungus con-tinues to develop throughout thefall, mild periods of the winter, andthe spring. The subcuticular hy-phae increase in diameter and innumber until they form stromate-oid layers which may extend overthe entire lesions. While these structures may consist merely ofsingle layers of cells, they are usually thicker, often developing intopseudoparenchymatous masses, six or eight cells deep (fig. 4). With the vigorous subcuticular development of the fungus, thecuticle is often slightly raised and at times broken, while the remains. , 4.—Longitudinal section of a lesion from anElberta peach twig of the preceding yearsgrowth, showing the abundant subcuticular de-velopment of the fungus and the vigorous pro-duction of conidiophores in the spring followinginfection. The host cells, which were badlydisorganized, are semidiagrammatically repre-sented. Camera-lucida drawing. (Magnified 310times.) PEACH SCAB AND ITS CONTROL. 11 of the dead epidermal cells are compressed inward in extreme casesuntil their identity is almost lost. In such cases the fungus oftengrows down between the epidermal cells, and occasionally hyphsepenetrate the intercellular areas of the first subepidermal layer. After the protective corky layers are fully formed, no furtherpathological anatomical changes occur. As the bark forms androughens with the second years growth of the twigs, the cuticle ofthe diseased areas partially sloughs off; and, as the bark thickenswith subsequent development, the lesions gradually
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