. Lectures on the evolution of plants. Botany; Plants. THE FUNGI 91. arrangement; but in all the higher ones they are borne in definite spore-fruits of characteristic form. This spore- fruit is undoubtedly, in many instances, the result of fertilization, being pro- duced by the formation of a peculiar cell, the archi- carp, which corresponds to the oogonium of the Phy- comycetes. This is usually fertilized by direct contact with the antheridium, and from it, more or less di- rectly, are produced the spore-sacs or asci. A good example of these simpler Ascomycetes is offered by the mildews which
. Lectures on the evolution of plants. Botany; Plants. THE FUNGI 91. arrangement; but in all the higher ones they are borne in definite spore-fruits of characteristic form. This spore- fruit is undoubtedly, in many instances, the result of fertilization, being pro- duced by the formation of a peculiar cell, the archi- carp, which corresponds to the oogonium of the Phy- comycetes. This is usually fertilized by direct contact with the antheridium, and from it, more or less di- rectly, are produced the spore-sacs or asci. A good example of these simpler Ascomycetes is offered by the mildews which infest many plants, Sphserotheca, the com- mon rose mildew. These are true parasites, but grow entirely upon the surface of the host, into whose epider- mal cells are sent suckers by means of which the parasite obtains nutriment from the host. The myce- lium of the fungus sends up vertical branches from which are successively cut off oval cells — spores or "conidia," — which germinate promptly and through whose means the fungus may spread rapidly. Fig. 24 (Ascomycetes). — A, a chain of conidia or non-sexual spores of a mildew (Sphserotheca), one of the simpler sac-fungi, or Ascomy- cetes, growing upon the leaves of the dandelion; B, the sexual repro- ductive organs, archicarp, ar, and antheridium, an; as the result of the fusion of these there is formed the spore-fruit, C, containing the single spore-sac, or ascus, sp, which is derived directly from the fertil- izer archicarp; D, the ripe spore- fruit seen from without; E, a single spore-sac containing eight spores; F, a cup-fungus (Ascobo- lus); G, section of the spore-fruit of Ascobolus showing the numer- ous spore-sacs, which are also derived from a fertilized archicarp; H, a single ascus of 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 th
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Keywords: ., bookcentury1900, bookdecade, booksubjectbotany, booksubjectplants
