. Comparative morphology of Fungi. Fungi. Fig. -Triphragmium Ulmariae. Types of cell fusion in the primary uredinium. (X 1,720; after Lindfors, 1924.) The difficulties are in part due to the fact that urediniospores some- times greatly resemble the aeciospores. They are 15 to 40 /z in diameter, unicellular, ovoid to cuneate, and generally finely echinulate or verrucoses, the membrane is generally fairly thick, hyaline to yellow brown, and pierced by several equatorial germ pores which are filled with a substance of variable composition. The number and position of the germ pores furnish i
. Comparative morphology of Fungi. Fungi. Fig. -Triphragmium Ulmariae. Types of cell fusion in the primary uredinium. (X 1,720; after Lindfors, 1924.) The difficulties are in part due to the fact that urediniospores some- times greatly resemble the aeciospores. They are 15 to 40 /z in diameter, unicellular, ovoid to cuneate, and generally finely echinulate or verrucoses, the membrane is generally fairly thick, hyaline to yellow brown, and pierced by several equatorial germ pores which are filled with a substance of variable composition. The number and position of the germ pores furnish important systematic characters. The urediniospores are easily separated from their stipes and are disseminated by winds, as are the aeciospores. Immediately after their maturity they are capable of germination, but lose this ability after a few months. True overwinter- ing of urediniospores is known with certainty in only a few cases, as in Uredinopsis Struthiopteridis and Kuehneola albida. In continental climates, they may have the opposite task of serving as resting spores during a drought. In all these cases, they possess a very strong brown wall, a persistent stipe and are called amphispores. Germination may take place within very wide limits of temperature, but the ability to infect lies within narrow limits, , in the neighborhood of the optimum for germination. At germination one or more germ tubes penetrate the stomata of the new host and there again develop a. 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 Gäumann, Ernst Albert, 1893-1963; Dodge, Carroll William, 1895-. New York [etc. ] McGraw-Hill Book Company, Inc.
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