96 



•which in the presence of oxygen becomes dark brown. Cultures have been 

 made in the fermentation tubes brought out by Dr. Theobold Smith, which 

 are so constructed that one arm of the tube remains free of all gases. In 

 such a tube the part of the culture in contact with the air becomes a deep 

 brown color and that in the opposite gas- free portion remains uncolored for 

 even a month or more, and its final change to brown, if the culture be con- 

 tinued suflSciently long, is without doubt due to diflfusion, both of the gas 

 absorbed from the air and the oxydized substance, by which they pass from 

 the open arm of the tube into. the closed arm. 



Prof. Bolley * has induced the scab on the sugar beets by irioculating with 

 the organism from potato scab. The scab has also been transmitted to the 

 beet directly from the potato, and also from soil in which pototoes affected 

 with scab had been grown, by experiments made in a cool greenhouse at 

 the Purdue station. In the former case a young potato tuber, just removed 

 from a pot-grown plant and well covered with active scab, was laid in contact 

 with a perfectly healthy root of a young beet. An examination was made 

 eight days later, but with no distinct evidence of results. A further exam- 

 ination thirty-seven days later showed a well defined scab about a quarter 

 of an inch across upon the beet, where the diseased potato touched it, and 

 no trace of scab elsewhere. In the latter case ten healthy beets were trans- 

 planted to pots containing soil in which potatoes affected with the scab 

 had been grown. These were examined sixty- four days after being trans- 

 planted, and eight of the ten roots were affected with the scab, five of 

 them having the neck entirely surrounded with it. 



The scabbing originates without doubt from the soil. How long the or- 

 ganism may maintain itself in the soil as a saprophyte is uncertain, but the 

 data elicited by Professor Bolley and by the Purdue station appears to show 

 that the time may extend over one or two years. 



The tissue of the roots is found to be blackened occasionally. This black- 

 ening is in the parenchymatous tissues between the rings of fibro- vascu- 

 lar bundles, and is of varying extent. It is sometimes found in roots that 

 are neither affected with the bacterial disease nor scab. 



There a^so occur small spherical or spheroidal masses that differ from 

 the rest of the interior tissue of the roots in having a uniform watery 

 appearance, similar to that of a water-core apple, and may, for the sake of 

 distinction, be called water-core spots. They occur in the parenchym- 

 atous tissue, and are sharply defined, not grading into the adjoining tissue. 



Bulletin N. Dakota Exper. Sta., No. 4, December, 1891. 



