368 Jones and Skive.—Influence of Ammonium Sulphate 
Hall, Miller, and Gimingham (12) ascribe the acidity of the acid soils 
of the Rothamstead grass plots that have been treated with ammonium 
salts to the action of various micro-fungi which are able to remove the 
ammonium-ion from a solution of its salts and set free the acids with which 
it was combined. 
Hoagland (14) made some studies in changes of reaction in nutrient 
solutions by barley seedlings, and says : ‘ In general it was found that 
alkaline solutions decreased markedly in OH-ion concentration, acid solu¬ 
tions decreased slightly in H-ion concentration, while neutral solutions 
remained practically constant. This must be the result either of the secre¬ 
tion of neutralizing substances by the plant, of chemical reaction with the 
material of the roots, or of selective absorption of specific ions.’ Later 
(15) with an ammonium chloride solution he found this solution increased 
in acidity after contact with plant roots. On continuing his studies (16), and 
applying quantitative chemical methods to the solutions before and after 
contact with plant roots, he concludes that ‘ in a complete nutrient solution 
it is impossible to say exactly what ions and undissociated salts are present 
before and after absorption by the plant. Such a system, with its various 
hydrolysable salts, is very complex. The resultant reaction is due to the 
particular state of equilibrium existing among all these constituents; and 
while we may determine the H-ion concentration with considerable accuracy, 
the data at present available do not enable us to determine the exact 
relations between the different components of the system.’ 
The plants were harvested, and the dry-weight values of tops and 
of roots were obtained in the usual way. The numerical data of yields 
of tops and of roots for each of the three series are presented in Table V in 
terms of the yields from culture T-^Cj in the respective series taken 
as unity, but the actual dry-weight yields of this culture are given in 
parentheses in grammes. The highest five yield values in each series (upper 
one-fourth) are indicated by bold-face type. 
From the data of Table V it will be observed that a large range 
in relative yield values occurs within each series, which may be attributed 
in the main to the variations in the relative salt proportions from culture to 
culture in the respective series, but since the low and medium yields have 
little that might be of interest or value in this connexion they will not here 
be considered. 
The relative yield values for the five cultures producing high yields of 
tops and of roots' in each series as given in Table V were plotted on the 
tetrahedral diagrams like that employed by Tottingham (37), but here 
presented in perspective in somewhat the same manner as was done by 
Espino ( 6 ). 
The high yield values of series E, F, and G are represented separately 
on the diagrams of Figs. 4 , 5 , and 6 respectively, areas of tops and of roots 
