282 MASS. EXPERIMENT STATION BULLETIN 171. 



and if the average for the plot were compared with those of the others in 

 the series it would appear clearly to be an illustration of the effect of 

 potassium on the formation of sugar; but there were two roots with 

 normal percentages of sugar from the plot, while there were roots in plots 

 5, 7 and 8 which were abnormally low where muriate of potash was regu- 

 larly applied in the normal quantity. It is the writer's opinion that these 

 variations in sugars on this group of plots may have been due to an attack 

 of rust in the summer of 1910, although special pains were taken to avoid 

 plants which had thus suffered, when the sample roots were selected. 



Furthermore, it is believed that there were two positively different 

 types of plants in these series in mode of growth, viz., one type with numer- 

 ous slender, long roots, and the other with fewer but thicker, fleshier 

 roots. This fact was not noted soon enough to correlate the observations 

 with the analytical data, but it is reasonable to assume that the slender 

 roots would have more epidermis in proportion to volume than the fleshy 

 roots, which renders it probable that the former would have more fiber 

 and less sugar than the latter. 



Organic Composition of Roots. 



Roots of 1908. 



