. A text-book of botany for secondary schools. Botany. FUNGI 145 as apple, pear, cherry, rose, hop, grape, wheat, gooseberry, cucumber, pea, verbena, sunflower, aster, etc. In fact, very few seed-plants seem to escape their attacks. Being exter- nal parasites, mildews are not necessarily destructive; but they often cause the death of the host. An examination of the my- celium shows that its filaments have partition walls; and hence the body is not ccenocytic, as in Mucor and Peronospora, but made up of a row of cells as in the Conferva forms among the green Algae. Small disk-like outgrowths ar
. A text-book of botany for secondary schools. Botany. FUNGI 145 as apple, pear, cherry, rose, hop, grape, wheat, gooseberry, cucumber, pea, verbena, sunflower, aster, etc. In fact, very few seed-plants seem to escape their attacks. Being exter- nal parasites, mildews are not necessarily destructive; but they often cause the death of the host. An examination of the my- celium shows that its filaments have partition walls; and hence the body is not ccenocytic, as in Mucor and Peronospora, but made up of a row of cells as in the Conferva forms among the green Algae. Small disk-like outgrowths are sent into the epidermal cells of the host, anchoring the mycelium and absorbing the cell contents. During the summer, numer- ous sporophores arise from the mycelium, not bearing sporan- gia, as in Mucor (§ 79), but forming spores in a peculiar way. The end of the sporophore rounds off, almost separat- ing itself from the part below, and becomes a spore. Below this another organizes in the same way, then another, until a chain of spores is developed (Fig. 135, A), easily broken apart and scattered by the wind. Falling upon other suit- able leaves, these spores germinate and produce new my- celia, enabling the parasite to spread with great rapidity. The mycelium produces also minute antheridia and oogonia, which come in contact with one another as do those of Peronospora (§ 80), but it is not worth while for the untrained student to try to observe them. As a result of. Fig. 134.—Lilac leaf covered with mildew, the shaded regions repre- senting the mycelium, and the ' black dots 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 Coulter, John Merle, 1851-1928. New York, D. Appleton
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1906
