1.8.0. 22 Proes. of the Asiatic Soc. of Bengal. [N.S., XVIII, 
The reason why this was not appreciated before is that 
previous calculations were based on the ash of the plants de- 
termined by ignition, which, however, gives too low an estimate, 
this being particularly true of the seeds, where the sulphur 
exists largely in the organic form in the protein molecule: for 
instance in rice grains there is 100 times as much sulphur 
trioxide as in the ash of that grain and forty times as much 
in corn and wheat grains as in their ash. 
ropping and drainage remove such quantities from the 
soil that, after fifty or sixty years, virgin soils unmanured or 
receiving but slight application during that period lose 40 per 
cent of the sulphur trioxide originally present. Normal soils 
again are poor in total sulphur trioxide. Consequently it 
should be applied occasionally as sulphate for the express pur- 
pose of maintaining in the soil an adequate supply of this 
element for crops rich in proteins. 
t is known that plants require the sulphur in the form of 
sulphates, and this is effected in the case of organic sulphur 
compounds by a process which embraces first the production of 
hydrogen sulphide by the means of ordinary decay bacteria, then 
the change of this to free sulphur and then to sulphates by a 
special set of what are now known as sulphofying bacteria. The 
sulphates thus produced are taken up by the plant proteins and 
thus a sulphur cycle is completed, just as is a nitrogen cycle, 
in plant economy. 
It now seems certain, after years of further experiment, 
especially in Oregon by Reimer, that sulphur must be claimed 
as an exceedingly important plant food, and that all or most 
of the benefits derived from acid phosphate can be secured by 
using gypsum, and a 50 per cent saving be made at. the same 
time. This artificial addition of sulphate, e.g. gypsum, to the 
soil also encourages the sulphofying bacteria to work more 
energetically ; and, that it additionally increases the growth of 
the nitrogen-fixing bacteria, seems established. 
The following statement briefly summarises a few concrete 
results (Mineral Industry, 1919, p. 332) :— 
‘*Gypsum increases the protein content in legume hays 
(alfalfa, clover, ete.). Professor Peterson at Wisconsin found that 
laster more than doubled the protein in alfaifa. Reimer con- 
where its use is comparatively new. . 
Small tonages were scattered through a great many sections 
for the first time during 1919, and the results secured were 5° 



