. The fungi which cause plant disease . Plant diseases; Fungi. 62 THE FUNGI WHICH CAUSE PLANT DISEASE. When covered, the chamber in which they are borne is called a perithecium, Fig. 39; when on an open disk the disk is called an apothecium, Fig. 101. According to their length of life spores are classed as: 1. rest- ing spores whose function is to tide over unfavorable conditions, hence the common name ''^ "winter spore," and in contradistinction: 2. "Summer spores" which are produced in abun- dance in warm weather, germinate immediately, and can ordinarily live but a short
. The fungi which cause plant disease . Plant diseases; Fungi. 62 THE FUNGI WHICH CAUSE PLANT DISEASE. When covered, the chamber in which they are borne is called a perithecium, Fig. 39; when on an open disk the disk is called an apothecium, Fig. 101. According to their length of life spores are classed as: 1. rest- ing spores whose function is to tide over unfavorable conditions, hence the common name ''^ "winter spore," and in contradistinction: 2. "Summer spores" which are produced in abun- dance in warm weather, germinate immediately, and can ordinarily live but a short time. In some species the spores that are to func- tion in water possess cilia, and the power of motion. These are zoospores or swarm spores, Fig. 44. At sporing time many kinds of fungi produce special structures for the bearing of spores. The fungous threads interweave to form a firm, or even a densely soUd, mass and constitute a false parenchyma. Such are the stalks and caps of the mushrooms and of the shelving toadstools, the skin of the puff ball, etc. A cross section of such a structure appears much as a true parenchyma, a longitudinal section shows it to be merely a mass of interwoven fungous threads. Sexual Spores are formed by the union of sexual elements, gametes. They are most conspicuous among the Oomycetes where the antheridium carries the sperms into the oogonium, fertilizes the obsphere and produces an oospore. Figs. 53-55. As a rule the sexual spores are produced toward the end of the vegetative period of the fungus. The asexual spores are produced eariier and for a longer period. Sexual spores are commonly resting spores. Germination of spores. Under suitable environment mature spores germinate and eventually give rise to vegetative bodies FiQ. 38.—Basidia of various ages. After Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustration
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfungi, bookyear1913
