Oct. i, 1920 Cause of Lime-Induced Chlorosis 35 



chlorosis. Green cane was found growing on a soil containing 76.70 per 

 cent calcium carbonate (19). 



Pears have frequently been reported as showing chlorosis on calcareous 

 soils (4, 6, 29, 38). 



Instances have been noted where a great many other plants have become 

 chlorotic on calcareous soils (24). Many of these cases are doubtless 

 more or less exceptional, since some of the plants do not become chlorotic 

 on most calcareous soils. Roux (39), without attempting a complete 

 compilation, mentions some 50 genera and species of cultivated plants, 

 ranging from mosses and orchids to maples and citrus trees, which have 

 shown chlorosis when planted on soils containing calcium carbonate. 



The results of the soil surveys and field observations seem to demon- 

 strate conclusively that this type of chlorosis is confined under field 

 conditions to calcareous soils. Probably no one species of plant, how- 

 ever, becomes chlorotic on all soils containing more than a certain per- 

 centage of calcium carbonate. Some plants are much more sensitive 

 to carbonate of lime than others — that is, they become chlorotic on soils 

 with lower lime contents and are less frequently found growing normally 

 on limy soils. 



The fact that plants very subject to chlorosis have been found in 

 a few instances growing normally on markedly calcareous soils shows 

 that the ability of calcareous soils to induce chlorosis does not depend 

 entirely on the percentage of carbonate of lime in the soil. This fact 

 also lends credence to the idea that it is not the carbonate of lime itself 

 that induces chlorosis but some condition usually associated with the 

 presence of carbonate of lime. 



RESULTS OF VEGETATIVE EXPERIMENTS IN WHICH CHLOROSIS WAS PRODUCED BY 

 NATURAL OR ARTIFICIAL CALCAREOUS SOILS 



Compared with the mass of observations on the natural occurrence of 

 chlorosis, there has been little reported in regard to inducing chlorosis 

 by the use of calcium carbonate or in regard to direct tests of calcifugous 

 plants in calcareous soils. There have been several vegetative experi- 

 ments with yellow and blue lupines, however, where the addition of 

 carbonate of lime to the soils caused a marked depression in growth and, 

 in some cases at least, induced chlorosis. Concordant, positive results 

 were secured by Heinrich (23), Meyer (32), Pfeiffer, and Blanck {35), the 

 Agricultural Chemical Experiment Station at Breslau (2), Creydt (5), 

 and Roux (39, p. 147-183). 



Biisgen (3) grew the calcifugous broom {Sarothamnus scoparius), 

 foxglove {Digitalis purpurea) , and heather {Calluna vulgaris) in artificial 

 calcareous and noncalcareous soils. The growth of all three plants was 

 moderately to greatly depressed in the calcareous soil, although only 

 broom was mentioned as showing chlorosis. 



