58 



PROTECTION OJ' PLANTS — 1924-25 



Testing the Nutrient Requirements by Triangulation. 



It was hoped that interesting variations might appear if the nutrient require- 

 ments were worked out after the method of Young and Bennet (9) and used 

 in 1923 by Scott (8) in working out the relationships of a group of cultures to 

 prove that they were all one Collectotrichum. A series of twenty-one cultures, 

 using potassium acid phosphate (monobasic), calcium nitrate and magnesium 

 sulphate were set up. The salts varied in the different solutions by increments 

 of one-eighth and had an osmotic concentration of three and one-half atm.osphe- 

 res. Sucrose was added in equal amounts 3.42 grams per 100 cc. of the cul- 

 ture, thereby giving the culture solution a total osmotic pressure of four ad one- 

 half atmospheres. 



In these triangles the individual cultures are numbered according to the 

 row in which they occur and according to their position in the row. The rows- 

 are numbered from the base to the apex of the triangle. The position in the tow 

 is from left to right. Thus the culture on the extreme left of the first row is 

 numbered 11, the second from the left in the third is 32, and in this way every 

 culture received a number. 



The method of arranging the concentrations is given in the following table. 



TABLE VII 



Showing the amounts to use in making up the flasks for the triangulation 



experiment. 



