. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 10 BULLETIN 395, U. S. DEPARTMENT OP Fig. 3.—Longitudinal section of a lesion from an Elberta peach twig of the current year's growth, showing the early subcuticular de- velopment of the fungus and a very early stage of cork ^formation. Camera-lucida drawing. (Magnified 310 times.) cork layers may be formed, before the final rapid swelling of tbe fruit prior to its matmi-ity. In such cases stresses are set up and cracks of varying sizes result. In many cases such openings are scarcely macroscopic, but on
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 10 BULLETIN 395, U. S. DEPARTMENT OP Fig. 3.—Longitudinal section of a lesion from an Elberta peach twig of the current year's growth, showing the early subcuticular de- velopment of the fungus and a very early stage of cork ^formation. Camera-lucida drawing. (Magnified 310 times.) cork layers may be formed, before the final rapid swelling of tbe fruit prior to its matmi-ity. In such cases stresses are set up and cracks of varying sizes result. In many cases such openings are scarcely macroscopic, but on badly diseased fruits, where the spots have become confluent, the cracks may ex- tend across an entire side of the peach and reach inward to the pit. Twig lesions.—In the early stages of twig infection, slender, branching, hyaUne, septate hyphss of the fungus are found penetrating the subcuticu- lar areas immediately exterior to the cellulose waUs of the epidermal cells (fig. 3). As the fungus develops, its ramifications become more general, its individual cells thicken, the un- derlying epidermal cells of the twig die, and the diseased areas are effec- tively cut off from the sound cortical tissues below by layers of cork cells. These corky layers are formed by means of tangential divisions of the subepidermal cells. It is not unusual, however, for the first division to be transverse, the daughter cells dividing tangen- tially. The two or three actively concerned hypodermal layers are, in each case, rapidly converted into a fairly uniform barrier of thin corky cells of meager proto- plasmic content. As the lesions age and the epidermal cells be- come more and more disorganized, the outer layers of subepidermal cells die and turn brown. After the advent of the dormant period of the host, the fungus con- Fig. 4.—Longitudinal section of a lesion from an +iTmp«i to dpvplon thmncrhmit thp, Elberta peach twig of the preceding year's tmues to aeveiop inrOUgUOUt tne gro,nh, sho
Size: 1908px × 1310px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauth, bookcentury1900, bookdecade1910, booksubjectagriculture
