MISSOURI BOTANICAL GARDEN BULLETIN 27 
tion, and the tops of these vessels are covered with paraffined 
paper. The latter supports the seed, and through punctures 
in the paper the growing roots are brought into the solution. 
Under suitable conditions the stems and leaves then grow 
normally, and the roots may almost fill the vessels. But be- 
fore describing some of the points which the experiments 
themselves are designed to show in detail, it is perhaps well 
to define briefly some relations of plants to the mineral con- 
stituents. 
The Necessary Minerals——In order to afford more or less 
perfect growth or development, the water cultures, such as 
those above mentioned, should contain in the form of soluble 
salts the elements nitrogen, phosphorus, potassium, calcium, 
magnesium, sulphur, and iron. The concentration of the total 
salts should be less than 1 part of the salts in 1,000 parts of 
water. The experiments displayed are arranged in eleven 
groups. In some of the groups three kinds of plants are em- 
ployed, while in others only one is used; in each case, then, 
one or more of the following: Canada field peas (Pisum 
arvense), horse beans (Vicia Faba), and corn (Zea Mays). 
The various groups and some general notes on the chief facts 
which they point out are enumerated below. 
Group I. The plants are grown in a full nutrient solu- 
tion—with all necessary mineral constituents present—: here 
normal growth occurs. The actual constitution of this solu- 
tion is as follows: 
eg ne Pega g ares piaree eee 4.0 grams 
Powmeaiam nitrates. fo. 26 5 6 Ae 1.0 gram 
Magnesium sulphate... 2.26.00. 2055: —. 
Potassium phosphate. ................000. 1628 
POUMGNRUUD: CHD 5 55 oa ek howe cas oes oe os. * 
AION CRIES cc o's 43 Saco tie aan ks trace 
MVGEOR..c 5 a5 055% a Linker une cay so wank 40 liters 
Contrasted with this are cultures in which the calcium salt 
(lime) alone is omitted, from which it is clear that a solution 
lacking this one constituent is in no way suitable for growth. 
Another culture lacking only the very important element 
nitrogen (as nitrates or compounds of ammonia) exhibits a 
checking of growth which is less marked, due in part, of 
course, to the fact that the seed leaves (cotyledons) furnish 
organic nitrogen in sufficient quantity for the early growth 
stages; but when the seed leaves are cut off a more marked 
diminution in growth occurs. Plants may be grown to 
maturity in solution cultures, if fresh solution is added oc- 
casionally. . 
