88 BOTANICAL GAZETTE [FEBRUARY 
Lawes and GILBert (36) found, in their fertilizer experiments 
with red clover, that ‘‘the produce was considerably increased by 
the application of gypsum, and still more so by that of the sul- 
phates of potash, soda, and magnesia, and superphosphate of lime.” 
In four years the increased yield from the use of gypsum was 3.5 
tons of dry hay, or an average of 0.9 ton per acre per year. 
Hunt (35), at the Pennsylvania Agricultural Experiment Sta- 
tion, used gypsum in a rotation of corn, oats, wheat, and hay 
(timothy and clover). Gypsum was applied at the rate of 320 
pounds per acre per rotation in two applications, 160 pounds to 
the corn and 160 pounds to the wheat. No other fertilizers were 
used, and no increases in yields were obtained from the use of 
gypsum. ‘These experiments would be more valuable if the gypsum 
had been applied to the clover and other fertilizers had been used 
to remove the possibility of another limiting factor. 
MitterR (51) grew clover in pots containing Oregon soils. 
Applications of sulphur were made in the form of flowers of sul- 
phur, sodium sulphate, and gypsum. Gypsum and sodium sulphate 
gave increased yields, but the flowers of sulphur had little effect. 
SCHREINER (61) studied the effect of different salts on oxida- 
tion in soil extracts in which wheat seedlings were grown. He 
reports increased oxidation from the use of calcium sulphate, 
potassium sulphate, and sodium sulphate. 
Dymonp, Hucues, and Jupe (18) compared the effect of 
ammonium sulphate and ammonium chloride on cabbages grown 
on non-calcareous soil. Greater yields were obtained with the 
ammonium sulphate than with the ammonium chloride. In their 
experiments with clover they obtained a 20 per cent increase in 
hay from the use of gypsum. In pastures they observed that 
legumes predominated where sulphates were applied, and grasses 
where no sulphates were used. Gypsum increased the yields of 
red clover, maize, and vetch in sand cultures, and of vetch in soil 
cultures. All the pots received applications of calcium and mag- 
nesium carbonates. 
LipMAN and GERICKE (40) compared the effects of different 
nitrogenous fertilizers on barley grown on Oakley’s vitro sand, and 
found the greatest increase with ammonium sulphate. When 
