346 Infusorial Earth and its Uses. 'July? 
other forms of silica, that is, in granular particles in the 
(Kunkel) straw, they being entirely replaced by diatoms. 
This leads to the conclusion that the diatom is the more 
acceptable for assimilation, and when sufficient infusorial 
remains are present, replaces any other divided form of 
silica. I have previously attempted to substitute silica 
for diatoms, as obtained from the decomposition of slags 
from iron furnaces, but have failed to derive any satisfactory 
results. This is due to its combination as a silicate; and 
when liberated by stronger acids, it agglutinates into masses 
too hard and large to be absorbed by the plant.” 
Prof. Wilson concludes his report in the following glowing 
terms: — “ I look upon this application of vegetable silica to 
fertilising purposes as the most important adaptation of 
matter for the reproduction of vegetation that has ever been 
discovered. It is the first step in a new direction, rationally 
conceived and judiciously carried out. Anew impetus will 
be given to the study of plant physiology, which will demon- 
strate that more than a heterogeneous mixture of elementary 
bodies and their compounds are required for the production 
of the crops beneficial to the requirements of man.” 
With regard to the foregoing statements and inferences 
of Prof. Wilson, while not attempting to undervalue their 
great interest and possible entire accuracy, the writer would 
remark that the demonstration of the presence of the infu- 
sorial forms in the structure of the wheat stalks proves 
simply that these bodies are sufficiently minute to enter the 
root capillaries and pass into the sap-cells of the plant — 
nothing more. It may possibly be that, once having entered 
the body of the plant, they are assimilated, and made to 
subserve to the fundtion of giving strength to the stalk ; or, 
as appears to the writer equally plausible, they may simply 
aCt as so many minute mechanical impurities drawn into 
the circulation of the plant, and, effecting a lodgment 
wherever they chance, clog up the passages, and thus actu- 
ally obstruct rather than serve the process of nutrition. To 
follow the history of one of these forms in a living plant 
under the microscope, and observe its gradual dissolution, 
would afford the only method of positively proving the 
truth or falsity of either of the explanations that have been 
presented. While not presuming to decide so doubtful a 
question, it is veiy reasonable to believe that much of the 
silica of the so-called silicated superphosphate is made 
“ available ” as plant-food in solution as an alkaline salt, in 
which condition its assimilation by the plant presents no 
difficulties to the understanding. Dr. Wolf, the excellent 
