. Nature and development of plants. Botany. 246 REPRODUCTION OF PERISPORIALES twelve generations, at which time he states that the spores would grow upon the untreated leaves. Perhaps this is the explanation of some epidemics or the occasional sudden appearance of a plant disease. A variety of circumstances might cause plants to form substances attractive to the parasite or to fail to develop repellent. Fig. 157. Sexual reproduction of a powdery mildew: A, meeting of the male, an, and female, 0, gametangia. B, fertilization, the male gamete, m, is seen approaching the female. C, section of you
. Nature and development of plants. Botany. 246 REPRODUCTION OF PERISPORIALES twelve generations, at which time he states that the spores would grow upon the untreated leaves. Perhaps this is the explanation of some epidemics or the occasional sudden appearance of a plant disease. A variety of circumstances might cause plants to form substances attractive to the parasite or to fail to develop repellent. Fig. 157. Sexual reproduction of a powdery mildew: A, meeting of the male, an, and female, 0, gametangia. B, fertilization, the male gamete, m, is seen approaching the female. C, section of young ascocarp showing the early germination of the gametospore, which has become surrounded by hyphae derived from the mycelium. D, later stage, the gametospore has developed several cells and the second cell from the end, as, will produce the ascus.—After Harper. materials. In either case they would become susceptible to the disease. The spores are formed in chains (Fig. 156, c) from the end of the erect hyphae that project from the surface of the leaf in thick masses, causing the powdery appearance and the popular name of these parasites. These spores germinate quickly and rapidly spread the fungus. The reproductive organs have in this group become still further reduced and appear as short branches as shown in Fig. 157, A. The solution of the walls at the point of contact of these organs permits the male gamete to pass over and fuse with the female (Fig. 157, B). The growth of the gametospore forms a limited number of cells and one of them, usually the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Curtis, Carlton Clarence, 1864-1945. New York, H. Holt
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