. Fungi, ascomycetes, ustilaginales, uredinales. Fungi. 200 PROTOBASIDIOMYCETES [ Fig. 170. Uromyces Poae'R&h&n.; aecidium just before the epidermis is broljen through, x 310; after Black- man and Fraser. Pliragmitis. A corresponding discoloration takes place around the young aecidia, and there is thus some suggestion that the spermatia, when functional, were carried to their destination by insects. The aecidia occur in groups, usually on the abaxial side of the leaf; in them the aecidiospores are produced in basipetal rows (fig. 170) alternating with small, abortive, intercalary c
. Fungi, ascomycetes, ustilaginales, uredinales. Fungi. 200 PROTOBASIDIOMYCETES [ Fig. 170. Uromyces Poae'R&h&n.; aecidium just before the epidermis is broljen through, x 310; after Black- man and Fraser. Pliragmitis. A corresponding discoloration takes place around the young aecidia, and there is thus some suggestion that the spermatia, when functional, were carried to their destination by insects. The aecidia occur in groups, usually on the abaxial side of the leaf; in them the aecidiospores are produced in basipetal rows (fig. 170) alternating with small, abortive, intercalary cells, by the disintegration of which they are set free. They may be carried to consider- able distances by the wind, and there is evidence that they are sometimes distri- buted by means of insects or of snails. The mature aecidio- spore is usually subglobose or polygonal in form, it is enclosed in a thick wall per- forated by several germ-pores, and contains red, yellow or orange pigment, and always two nuclei. In germination a hypha is put out which enters the host plant through one of the stomata and so penetrates into the inter- cellular spaces. The development of the aecidium begins by the mass- ing of hyphae either deep in the tissues of the host {Gyin- nosporangium clavariaefonne, Puccinia Poarnin (Blackman and Fraser '06), Pitccinia Falcariae (Ditt- schlag '10)), or directly below the epidermis (JPhragmidium violaceum (Black- man '04), Uroviyces Poae (Blackman and Fraser '06) (fig. 171), Puccinia Claytoniata (Fromme '14)); these hyphae give rise to a more or less regular series of uninucleate cells. These are the fertile cells, but, before developing further, each, at any rate in the relatively primitive forms (caeomata), may cut off one or occasionally more terminal sterile cells which ultimately degenerate. The fertile cells may unite laterally in pairs (fig. 172), so that binucleate compound cells are formed ; they may similarly pair with the. Please note that these i
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectfungi, bookyear1922
