58 
AMERICAN JOURNAL OF BOTANY 
[Vol. 9 
The pH value at the end of the first week is also given. The water loss by 
transpiration is given for the entire growth period. The average daily 
loss from the white and black atmometers w^as 5.83 cc. and 6.49 cc, re- 
spectively. 
IV. The Effect of Iron and Aluminum Salts Upon Growth in Solution "H" 
(a) Solution Cultures. As solution "H" has been previously described, 
only a brief account of the experiment and the environmental conditions 
will be given here. The pint jars and 450 cc. of the culture solutions were 
used in all cases. Series i was run for 37 days during January and February. 
Conditions for growth at the beginning of the experiment were not very 
c ^ //-5 //-/y n-crtt5 rttfs r-/y r-c as a-/v /\-c h-s H-f^ h-c Fttt^ r -N f-c as /»-// /»-c 
0.0002./V o,ooQ6/y. 
Fig. 4. Relative weight of tops and H-ion concentration before and after growth, in 
solution " H " as they were afifected by the addition of acids and salts in 0.0002 iVand 0.0006 
N concentration. In this and the following figures, the following notation is used: C, 
control; F, and A denote the cations H, Fe, and Al. The anions are indicated thus: 
5 = SO4; N = NO3; C = CI. Ferrous and ferric sulphate are distinguished by plus signs; 
7*"++ 5 = ferrous sulphate, 7^+ + + 5 = ferric sulphate. 
favorable. Conditions were very favorable for growth during the 37-day 
period in which series 2 was grown. The plants grew rapidly and seemed 
to be in excellent condition until several days before the end of the experi- 
ment, when the leaves of some of the plants were unable to open because of 
the formation of a mucilage-like substance. This was most noticeable in 
the solutions containing aluminum. This pathological condition was 
associated with a number of bright sunny days during which it was im- 
possible to keep the greenhouse temperature below 32° C. It never ex- 
ceeded 35° C. The relative transpiration is given for series 2 and is based 
upon the transpiration for the last week of growth. During this period the 
average daily loss from the white and the black atmometers was 11. 4 cc. 
and 13.6 cc, respectively. 
