268 



Journal of Agricultural Research 



Vol. XIX. No. 6 



of smut spores were thrown up into the opening at i in figure i , and an 

 attempt was made to catch any which went through the drum upon 

 moistened sterile cotton held at h. This cotton was then washed and the 

 water carefully examined with the microscope. No spores could be 

 found upon this cotton, although the experiment was repeated several 

 times. Every time the room was entered the space between the double 



doors was thoroughly 

 sprayed, and a rubber 

 coat which was kept 

 hanging in this ante- 

 chamber was put on. 

 Although wheat was 

 grown in the adjacent 

 houses and became 

 badly infected with 

 mildew {Erysiphe gra- 

 minis) none appeared 

 on that grown inside 

 of the isolated room. 

 Neither did any aphids, 

 which were plentiful at 

 various times in other 

 rooms in the green- 

 house, make their way 

 into the isolated room. 

 The soil used in these 

 experiments was in 

 every case sterilized, 

 and only boiled water 

 -/ V I was used for watering 



^ /* until after the lake 



^S from which the water 



Fig. I.— Diagram of air-washing apparatus for isolated room used for SUpply WaS deriveu 

 growing rust- infected seed: (a) Hose connection; (6) spray nozzle; (c) ^vg^g frOZCU OVCr. 

 galvanized iron cylinder; ((/) greenhouse gutter into which the water f1 + f 



from spray drained; (e) connection pipe from cylinder to blower; rOUr aluerent iOtS OI 

 (/) electric blower; {g) floor of greenhouse; {h) mouth of the blower j-ysted SCCd WCrC grOWn 

 where air entered the room; (i) air intake. . t-a j. i.- •„ 4-u:„ 



at different times in this 

 house. Bach lot was sown in flats 12 inches wide, 24 inches long, and 

 6 inches deep. These experiments will now be considered in the order 

 in which they were performed. 



Experiment i. — Seed for this experiment was selected from lots of 

 wheat obtained from the following sources: Four varieties of durum 

 from the cereal- disease plots at Madison, Wis.; one lot of Marquis from 

 Maynard, Iowa; one mixed lot of wheat from Leith, N. Dak.; one lot of 

 durum from Brookings, S. Dak.; one mixed lot of unknown source from a 



