Nature and development of plants . Fig. 145. Fig. 146. Fig. 145. Appearance of one of the powdery mildews, Uncinula, on leafof elm. Fig. 146. Enlarged view of the mycelium, ascocarp, etc., of one of themildews, Erysiphe: c, erect hyphae forming spores or conidia; h, haustoriapenetrating epidermis of leaf; a, ascocarp or Fig. 147. Sexual reproduction of a powdery mildew: A, meeting of themale, an, and female, 0, gametangia. B, fertilization, the male gamete, m,is seen approaching the female. C, section of young ascocarp showing theearly germination of the gametospore, which has be
Nature and development of plants . Fig. 145. Fig. 146. Fig. 145. Appearance of one of the powdery mildews, Uncinula, on leafof elm. Fig. 146. Enlarged view of the mycelium, ascocarp, etc., of one of themildews, Erysiphe: c, erect hyphae forming spores or conidia; h, haustoriapenetrating epidermis of leaf; a, ascocarp or Fig. 147. Sexual reproduction of a powdery mildew: A, meeting of themale, an, and female, 0, gametangia. B, fertilization, the male gamete, m,is seen approaching the female. C, section of young ascocarp showing theearly germination of the gametospore, which has become surrounded byhyphae derived from the mycelium. D, later stage, the gametospore hasdeveloped several cells and the terminal one is being transformed into anascus, as.—After Harper. 214 CLOSED TYPE OF ASCOCARPS contact of these organs permits the male gamete to pass overand fuse with the female (Fig. 147, D). The growth of thegametospore forms a limited number of cells, one or more ofwhich develop into asci (Fig. 147, C, D). As in Penicillium,this growth becomes enveloped by a mass of hvphae that originatefrom the mycelium. These ascocarps appear at maturity asblack specks and in the majority of forms they are provided withhair-like outgrowths that are very regular and characteristicof the genera (Fig. 148). The ends of
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