. Bulletin. Natural history; Natural history. DiSKASKS OF Gkaix Chofs, 1922-1926 91 states, essentially, that "nther conditions lieing equal, the variation in the time of occurrence of a given periodical event ... is at the general aver- age rate of 4 days to each 1 degree of latitude. ."> degrees of longitude and 401) feet of altitude, later northward, eastward, and upward in the spring and earlv summer, and the reverse in late summer and ; In accordance with this view, the State of Illinois has l)een divided into the sections shown in Figure 102, which represent theo
. Bulletin. Natural history; Natural history. DiSKASKS OF Gkaix Chofs, 1922-1926 91 states, essentially, that "nther conditions lieing equal, the variation in the time of occurrence of a given periodical event ... is at the general aver- age rate of 4 days to each 1 degree of latitude. ."> degrees of longitude and 401) feet of altitude, later northward, eastward, and upward in the spring and earlv summer, and the reverse in late summer and ; In accordance with this view, the State of Illinois has l)een divided into the sections shown in Figure 102, which represent theoretical time variates of periodical events in harmony with adjacent states. The slant- ing longitudinal lines represent a difference of approximately four-fifths. Fio. 102. Theorkticai. lines for , aimouding to Hopkix's \Tic Law The earliest wheat leaf rust infection occurs in the south, and at a given latitude infection earlier in the west than in the east. The seasonal progress of infection is in the northeasterly direction taken by the longitudinal lines. The horizontal lines represent, from south to north, a difference of one day, and the longitudinal lines a difference of four-fifths of a day, from west to east, in the appearance of first rust infections. When the first infection is observed in the south, the date of its appearance in any more northern region can be predicted 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 Illinois. Natural History Survey Division. Urbana, State of Illinois, Dept. of Registration and Education, Natural History Survey Division
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Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
