118 Botanical Department. [Bulletin 108 



average number of ties per mile is shown to vary from 2689 to 3148, 

 with a general average of 2800. This would make a total of 535,- 

 668,000 ties in track in the United States in 1899. The percentage 

 of the ties renewed each year varies considerably with the tie used, 

 the amount of the local rainfall, and the summer temperature, since 

 the growth of the timber-destroying fungi is most rapid in warm, 

 humid climates. With white-oak ties, by far the most desirable in 

 general use hitherto, the annual renewals in the north central states 

 will average about 280 to the mile, or about ten per cent, of the total 

 in track. 



For example : The Vandalia line, operating through central and 

 southern Illinois and Indiana, had 2,362,700 ties, all of white oak, in 

 its 833.16 miles of track on June 30, 1900, an average of 1840 ties per 

 mile. Of these, 237,157, or ten per cent, of the total, were removed in 

 that year. 



The Wabash railroad (Detroit division), operating 348 miles of 

 road ( sidings included ), had in track June 30, 1900, 1,040,000 ties, of 

 which all but 20,000 were white oak. Of these, 107,064, all of oak, 

 were renewed during the year ending on the above date, making the 

 per cent, of renewals during the year to the total of ties in track 10.3. 

 As this is a main line from Detroit to Chicago, with a gross tonnage 

 of 5,771,000 of rolling-stock passing over the track, and since the cli- 

 matic conditions of the region through which the road runs are typ- 

 ical for a large area in the North Central states where a very heavy rail- 

 road business is done, the figure of ten per cent, may be considered a 

 safe estimate of the number of white oak ties unfit for use on main 

 lines and calling for removal each year, in roads operating west of the 

 Alleghanies, east of the Mississippi, and north of the Ohio river. 



The Kansas City, Fort Scott & Memphis railroad, operating through 

 eastern Kansas, southeastern Missouri, northeastern Arkansas, and 

 Mississippi, into northwestern Alabama, operating 1278 miles of road, 

 laid with 4,623,044 ties, all of white oak, is reported as having re- 

 newed 527,337 in the year ending June 30, 1900. This slightly higher 

 average of thirteen per cent, is what would naturally be expected, 

 when the greater annual rainfall and the higher mean annual tempera- 

 ture of the greater portion of the region traversed are taken into con- 

 sideration. 



On the other hand, the Santa Fe, Prescott & Phoenix railroad, 

 operating 145.17 miles, through the elevated arid region of northern 

 Arizona, with 678,000 ties in track, all of pine naturally in humid 

 regions a very perishable wood renewed only 63,734 ties eight per 

 cent. bringing the pine for this road up to the standard of oak as a 

 tie timber, on account of the exceedingly dry local climate, in which 



