R. S. DUNHAM 



199 



apparent that all three varieties showed the greatest response when 

 started in the warm room and transferred to the cool chamber and the 

 least, even at high dosages, when started in the cool chamber whether 

 they remained there or not. Varietal differences are also apparent in this 

 treatment. 



TABLE 1 



Comparison of increase in height of untreated flax and yield of seed from flax 

 sown the same day and sprayed at four stages of growth (Experiment i) versus 

 untreated flax and flax sown on four dates and sprayed on the same day 



(Experiment 2). 



*Morpholine salt of 2,4-D. 



An experiment now in progress at Minnesota by Shulstad, Dunham, 

 and Heggeness indicates that the rate of increasing height differs among 

 flax varieties; that this rate differs for the same variety when sown at 

 ten-day intervals; and that the order of varieties ranked according to 

 rate of increase in height varies with different planting dates. The 

 experiment has not been completed, but there is also evidence that 

 varieties rated on the basis of tolerance to 2,4-D under a given set of 

 growing conditions do not necessarily maintain that order under a 

 different environment. 



It appears from all the evidence available that rapidity of growth is an 

 important factor in determining the susceptibility or tolerance of flax 



