412 BOTANICAL GAZETTE [JUNE 
that the amounts of H,SO, thus produced would be so enormous as 
to make it useless, since the demand for the acid is as yet quite 
limited. It has been suggested, therefore, among many other 
proposed uses for it, that H,SO, be used in small quantities in the 
irrigation water to act as a solvent for soil minerals. It was this 
idea which suggested the preliminary experiment described below, 
along with the others, on the effects of the metallic salts on plant 
growth. ' 
Experiments 
The soil employed in the experiments was a light sand with a 
good humus supply, and was constituted chemically as follows: 
Insoluble residue. ...... ee tp er cent MnO... ci. sei... ©.o1 per cent 
os ee ae 2.94 [5 Re ae 0. 26 
RAE grag ae ogres eee 2.05 0.36 
Re see: 3.38 1) See aera ae 0.17 
eS es 1.59 ee ia as 0.45 
Bes ee ook oes s 0.02 we. pees 2.35 
Large 8-inch flower pots were filled with 12 lbs. of soil and 
treated with varying amounts of the solution of the salt to be 
tested, each cc. representing a known weight of the salt. The con- 
centrations employed are noted in the tables in parts per million 
of water free soil. The plants tested were the vetch (Vicia sativa) 
and the Little Club variety of wheat. Eight seeds, which were 
carefully selected, were planted in each pot, and after some growth 
was made were thinned to 4 plants per pot. The pots were care- 
fully irrigated so as to give the soil an optimum moisture content 
but not allow any moisture to percolate from the soil, thus prevent- 
ing loss of the salts tested. The plants were all grown under glass 
and appeared to make good vigorous growth from the start. The 
appearance of the aphis and other insects in large numbers undoubt- 
edly had something to do with diminishing the total yield of dry 
matter, but not enough to affect the results seriously. The vetch 
was not allowed to mature, but had to be harvested about the same 
time that the wheat was cut, because the mildew had attacked the 
plants rather seriously. The wheat was mature, however, when 
harvested. In the case of the vetch, the weight of the tops, as well 
as that of the roots, is given, while in the case of the wheat, only the 
