STEWART'S DISEASE OP SWEET CORN (MAIZE). 



121 



have no evidence of any general distribution of this organism in agricultural soils, rather 

 the contrary, outside of districts where sweet-corn is grown, and since in many bacterial 

 diseases, both plant and animal, we have an enormous amount of evidence tending to show 

 that the pathogenic bacteria are not carried far by the wind ; or, if so carried, do not induce 

 disease. 



I reasoned as follows: If the case or cases of this disease at Takoma Park and those 

 which appeared in the trial-rows on the 

 Flats were due to local causes, i. c, to 

 organisms already present in the soil, 

 and not to infected seed, then the plants 

 grown from the same lot of seed-corn 

 on Arlington Farm should be healthy. 

 If, on the contrary, Bacterium stevuarti 

 was present in a living condition on any 

 great number of the kernels, then the 

 result would be the same as at Takoma 

 Park and in the trial-rows, i. e., many 

 cases of the disease, and the disease 

 would appear first in those varieties 

 carrying the organism into the field, 

 however much it might become infec- 

 tious to neighboring varieties later in 

 the season. 



The second of these two supposi- 

 tions is exactly what happened. My 

 notes on this experiment are as follows : 



SERIES XI TO XV, 1903. 



About 3 acres of sweet corn were 

 planted at the Arlington Farm on July 29 

 and 30. The seed came from Mr. Pieters, 

 and was the same as that used for his trial 

 rows, i. e., of same origin. The ground was 

 not in very good condition, not having been 

 harrowed enough. The land slopes gently 

 from east to west. There is a ditch on the 

 west side and the west end is perhaps 25 feet 

 lower than the east end. The rows ran east 

 and west. The plots were not check-rowed, 

 but seed was dropped by hand, the hills 

 being made about 3 feet apart. Five 

 standard varieties of corn were planted 

 Old Colony, Potter's Excelsior, Cosmopoli- 

 tan, Country Gentleman, and Crosby's Fig. 53.* 

 Early. Beginning at the south end, the 



plots were as shown in table 10 (between the plots a row was skipped, making a distance of 6 feet 

 only between varieties). 



The italicized varieties are those suspected of harboring Bad. stevuarti on their kernels. 

 The other varieties are some of those which were nearly or quite free from disease in Mr. 

 Pieters's trial-rows on July 2 1 and were not suspected. On leaving the city for the summer 

 the writer left word to have them re-examined in August, but unfortunately this wasnotdone. 



*Fig. 53. Inner husks of Golden Bantam sweet-corn, showing yellow spots (black areas) due to Bacterium 

 stewarti. Vascular system badly diseased. Slime oozing on the kernels. A natural infection obtained by planting 

 diseased seeds which formed part of a Congressional seed distribution. Hot-house experiment of 1908 (see text). 



