J917] Ayres: Nutrient Solution on Plants Grown in Sand Cultures 353 



Dry "Weight in Series I 



A comparison of the curves for height (fig. 1) and for dry 

 weight (fig. 3) shows that in a general way height is an index to 

 the dry weight. This fact is more marked in this series than 

 in either series II or III since the plants were more uniform 

 throughout the series, being uniformly stocky where the height 

 was above 40 cm. In the other groups some of the plants were 



Decigrams. 

 Dry wt. of tops 



110 

 100 

 90 

 80 

 70 

 60 

 50 

 40 

 30 

 20 

 10 



.001 .01 .05 .1 .15 



% NaNOa 



Fig. 3. — Graph showing influence of equal quantities of NaNO^ in fhe 

 different groups of series I upon dry weight of tops. 



tall and very spindly (pi. 15), and there was a marked decrease 

 in the length and width of leaf, which would, of course, lower 

 the dry weight. The height measurements even on a plant of the 

 habit of the tobacco cannot be taken alone as an indication of 

 the nutritive value of a solution, a fact which has been shown to 

 hold true to a much more noticeable extent in such plants as 

 wheat, which will stool more in some cultures than in others 

 without perceptible differences in height. 



The effect of the concentration is evidenced in the curve for 

 group D, which is much higher for plants 3 and 4 than for plants 

 of like number in any other groups. Had it been possible to take 



