32 
The results in brief were: The check plants made a good green 
growth; the plants in the pots with sodium carbonate were greatly 
depressed in growth; those in the pots with 0.10 per cent of Na,CO, 
making scarcely any growth; but all plants maintained a good dark 
green color. 
It is, then, evident that it is not alone the soil alkalinity that 
causes the chlorosis. While the alkalinity produced by 0.01 per cent 
of Na,CO, is sufficient to greatly depress the growth of the plant, it 
disturbs the nutrition in a very different manner from CaCO,, as it. 
apparently has no effect on the formation of chlorophyll. 
In the experiment with calcium sulphate, or gypsum, soil No. 18 
was used. Five check pots received no gypsum, five pots received 
sufficient gypsum to give the soil a content of 5 per cent CaO, five 
gypsum to a content of 10 per cent CaO and five gypsum to a content 
of 15 per cent CaO. The results are given in the following table: 
Results of experiment in which gypsum was added to loamy soil. 





Average 
Content of CaSO4.2H2O and CaO in soil. Appearance of plants. weight of 
5 plants. 
Grams. 
Cheeks so o56:s tc ceste oa eet Pee Green throughout the experiment................- 604 
15 per cent CaSO,4.2H20, equivalent to |..... DO esd cle pe wtactecen ccselscumswsas cer meceacioncese 482 
5 per cent CaO. 
30.65 per cent CaSO..2H2O, equivalent |..... Oech ias Bue sate mole ita te ae sey me tase 452 
to 10 per cent CaO. 
45.98 per cent CaSO4.2H20, equivalent | Plants poorer color than others throughout the 470: 
to 15 per cent CaO. experiment, though not chlorotic. 


It appears that while the heavy application of gypsum depressed 
the growth, like the sodium carbonate it failed to produce the 
chlorosis. 
Since, then, it is neither the alkalinity alone nor the large amount 
of assimilable lime that induces the chlorosis, it would seem that the 
chlorosis is induced by both these factors working together. These 
factors may act directly on the plant or indirectly, by their effect on 
some of the nutrients contained in the soil. 
TREATMENT OF CHLOROTIC PLANTS WITH IRON AND OTHER 
SALTS. 
A number of experiments were made to overcome the chlorosis. 
Chlorotic plants growing in pots of calcareous soil were treated in 
various ways. Watering with Knop’s nutrient solution was inef- 
fective. This was partly to be expected, as heavy applications of 
nitrogen, potash, and phosphoric acid were found unavailing in check- 
ing the chlorosis. Additions of magnesium sulphate to the soil at 
intervals gave no result. If an unfavorable ratio of lime to mag- 
nesium-were the cause of the trouble, this treatment should have 
proven beneficial. 
[Bull. 11] 
