. Botany for high schools. Botany. Fig. 218. Ripe oospore of Peronospora aisinearum. Candida) is very common on the shepherd's purse, deforming the stems, leaves, flowers, and fruit. The mycelium is intercellular, and branched haustoria penetrate the cells. 419. Asexual stage.— The sporophores are short, are developed in great numbers, and crowded un- derneath the epidermis. These sporophores bear chains of spores (conidia; fig. 219), and the mass bursts through the epi- dermis, giving a white rusty appearance. The spores germinate by the formation of zoospores as in the grape downy mildew. 43
. Botany for high schools. Botany. Fig. 218. Ripe oospore of Peronospora aisinearum. Candida) is very common on the shepherd's purse, deforming the stems, leaves, flowers, and fruit. The mycelium is intercellular, and branched haustoria penetrate the cells. 419. Asexual stage.— The sporophores are short, are developed in great numbers, and crowded un- derneath the epidermis. These sporophores bear chains of spores (conidia; fig. 219), and the mass bursts through the epi- dermis, giving a white rusty appearance. The spores germinate by the formation of zoospores as in the grape downy mildew. 430. Sexual reproduction.—This process is very much as described for the downy mildews, but in some species many sperm nuclei from the sperm case enter the egg and pair off to fuse with the many nuclei in the egg. 431. Formula* for the life history of the water molds and downy mildews. This can be written as fol- From Cystopus candidus, conidial stage. A, tuft of loWS, Starting with the conidiophores sorus, showing a few conidia in chains; ^ ^ ^ 5, conidia forming swarm spores or zoospores; C, zoo- fertilized egg! Fertil- spores, some of them germinating; Z), germinating zoo- . spores, the hvphce about to enter stoma. (After De ized e2f£f — Plant — asex- Bary.) ' ual spores repeatedly formed — / sperm gamete \ f^j-^jij^ed eojg, etc., and can be ab- ^ egg gamete ^. Fig. 219. * Not to be memorized. Introduced to represent graphically the life 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 Atkinson, George Francis, 1854-1918. New York, H. Holt and Company
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1910
