438 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9, 
when grown under different environmental conditions. Those plants which 
had a higher nitrate substrate for growth had a relatively smaller dry- 
matter content, while the reverse is true with those having less nitrates 
available. This is clearly brought out in the figures under consideration 
(table 8), and more clearly still in table lo. It would appear that metabolic 
processes such as respiration — not accompanied by increase in dry matter, 
but accompanied by an accumulation of aqueous or other volatile material — 
are accelerated in consequence of the larger available supply of nitrates. 
Physically, plants growing under such conditions take on the character of 
greater succulency. 
The green weights were not determined for the 44-day-period cultures, 
but the dry weights are essentially as in Series i, with a relatively higher 
dry-matter content for the low-nitrate cultures and a strong indication of 
an increased utilization of food in respiratory processes in the cultures in 
the high-nitrate solution. 
Measurements were made of length of roots for the 20- and 44-day 
periods respectively in order to determine whether or not the differences in 
nitrate content of the solutions had any stimulating effect on length. While 
the average lineal growth is somewhat higher in solutions with larger 
nitrogen content, the difference is not large enough to be significant (table 
8). It is interesting, however, to note that these root tips have continued 
to grow through a period of 44 days, increasing considerably in length, 
as is shown in the table, but showing little or no increase in total dry matter. 
Experiment VI 
Effect of Increased Nitrates upo?i Growth in Length 
of Isolated Tips of Radish Roots 
Germination of the seeds and preparation of the root tips for these 
cultures were carried out in the same manner as that described for corn. 
The cultures ran for 15 days. 
The results are given in table 9. They show no striking response in 
length of root of this plant to the increased nitrate content of the solution. 
Table 9. Radish; Results of 75 Days' Growth {Lengths in Centimeters) 
Culture 
Solution I 
Solution II 
Solution III 
(Low N.) 
(Medium N.) 
(High N.) 
I 
9 
12 
9.5 
2 
7 
7-3 
6.3 
3 
5 
20.5 
12.5 
4 
7.5 
13-5 
8 
5 
II 
6 
8 
Mean 
8 
II. 8 
8.8 
