RESULTS OF EXPERIMENTS. 9 



die of the third leaf when the fourth leaf was about one-fifth the 

 length of the leaf sectioned. Measurements were made of the thick- 

 ness of the cuticle and outer wall (taken together) and also of the 

 length and height of the cells of all epidermal cells in a transverse 

 section between the third vein (counting the midrib as one) and the 

 fourth vein on both the upper and the lower surfaces of the leaf. 

 The filar micrometer was used in making the measurements. 



The outer walls of the epidermal cells were measured together with 

 the cuticle because in these young plants the latter is so thin that 

 accurate measurements of the cuticle alone could not be made with- 

 out the expenditure of a great amount of time. Careful preliminary 

 measurements, however, were made of both the cuticle and the outer 

 epidermal cell wall independently, the cuticle and cell wall being 

 differentiated by staining with chloriodid of zinc. As a result it 

 was found that the thickening had taken place chiefly in the cuticle 

 and not in the cellulose zone of the cell wall. In the case of each plant 

 species grown in each of the soils containing different concentrations 

 of soluble salts as well as in the control soil, about 100 measurements 

 of the cuticle and outer wall of the epidermal cells were made on 

 both the upper and the lower leaf surfaces. Averages of the whole 

 number of measurements are given in Table I. 



In a similar manner measurements were made of the length and 

 the height of the epidermal cells on both the upper and the lower leaf 

 surfaces of each plant species grown in the soils containing different 

 concentrations of soluble salts and in the controls. (Tables II and 

 III.) 



RESULTS OF EXPERIMENTS. 



EFFECT OX THE FORMATION OF BLOOM. 



The growth of the plants was retarded by the amount of soluble 

 salts present. Wheat and oats made a slow growth in the soil con- 

 taining 2 per cent of total salts (1.4 per cent sodium chlorid) and bar- 

 ley failed to germinate at this concentration. Seedlings of all three 

 species grown in the soil containing 1.5 per cent of total salts (1 per 

 cent of sodium chlorid) made a better growth, but were^ very weak. 

 Seedlings grown in a soil containing 1 per cent total salts (0.7 per 

 cent sodium chlorid) did fairly well, but were still decidedly inferior 

 to the controls. Under natural conditions many agricultural plants, 

 especially cereals, are unable to endure a soil content of more than 

 1 per cent of sodium chlorid, and even a considerably less amount 

 will usually produce imperfect development. 



Soon after the plants in the saline soils appeared above the surface 

 of the soil they took on a dark bluish-green color, evidently due to 

 49297—08 2 



