File:A text-book of mycology and plant pathology (1917) (14594037758).jpg

Identifier: textbookofmycolo01hars (find matches)
Title: A text-book of mycology and plant pathology
Year: 1917 (1910s)
Authors: Harshberger, John William, 1869-1929
Subjects: Plant diseases Fungi
Publisher: Philadelphia, P. Blakiston's Son & Co
Contributing Library: The Library of Congress
Digitizing Sponsor: Sloan Foundation

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35). Family 3. Peronosporace.^.—This family is rich in parasiticforms which may be accounted as the cause of important diseases ofcultivated plants. The hyphte of the mycelia are irregularly and copi-ously branched and are found mainly in the intercellular spaces of thehost tissue sending short branches called haustoria into the adjoiningliving cells. These haustoria maybe glohvXax (Albugo = Cystopiis),club-shaped (Peronospora corydalis), branched (Plasmopara) (Fig. 36),or branched and snarled (Peronospora). Septa are absent except 1 Petersen, Henning E.: An Account of Danish Fresh-water Phycomycetes.Annales Mycologici, viii, No. 5, igio. 112 MYCOLOGY when the reproductive organs are formed. Non-sexual spores, orconidiospores, are borne on conidiophores which may remain withinthe host (Albugo = Cystopus), or grow beyond the surface. They maybe. either simple or branched. These conidiospores either germinate,as in Phytophthora infestans and Peronospora nivea by means of zoo- ^,^„^
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Fig. 35.—I, Zoosporangium of Achlya racemosa; 2, escape of zoospores; 3, fly-covered by mycelium; 4, zoospores of fungus; 5, Achlya ferax with zoosporangia andzoospores; 6, Achlya prolifera, 24 hours after germination of zoospores. 7, Achlyamonoica, with antheridia and oogonia; 8, Achlya conlorla. (After Henri Coupin,Atlas des Champignons Parasites et Pathogenes de VHomme el des Animaux, pi. xviii,1909.) spores which escape or by the protoplasm escaping (plasmatoparous), asin Peronospora densa, or by germ tubes, which in some species (Perono-spora lactuccB) appear at the end of the spore (acroblastic), or at theside of the conidiospore (pleuroblastic), as in Peronospora radii. Theoogonia and antheridia, which are also present, are formed in the OOSPORE-PRODUCING ALGAL FUNGI 113 tissues of the host. The different kinds of nuclear fusion, whichaccompany fertilization, have been described previously. The oospore,which is formed, acts as a zoosporangium in some cases for it givesrise to

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