* My son, George Darwin, has calculated for me the diameter of a sphere
of phosphate of ammonia (specific gravity 1.678), weighing the
one-twenty-millionth of a grain, and finds it to be 1/1644 of an inch.
Now, Dr. Klein informs me that the smallest Micrococci, which are
distinctly discernible under a power of 800 diameters, are estimated to
be from .0002 to .0005 of a millimetre that is, from 1/50800 to
1/127000 of an inch in diameter. Therefore, an object between 1/31 and
1/77 of the size of a sphere of the phosphate of ammonia of the above
weight can be seen under a high power; and no one supposes that odorous
particles, such as those emitted from the deer in the above
illustration, could be seen under any power of the microscope.) [page
174]
CHAPTER VIII.
THE EFFECTS OF VARIOUS OTHER SALTS AND ACIDS ON THE LEAVES.
Salts of sodium, potassium, and other alkaline, earthy, and metallic
salts Summary on the action of these salts Various acids Summary on
their action.
Having found that the salts of ammonia were so powerful, I was led to
investigate the action of some other salts. It will be convenient,
first, to give a list of the substances tried (including forty-nine
salts and two metallic acids), divided into two columns, showing those
which cause inflection, and those which do not do so, or only
doubtfully. My experiments were made by placing half-minim drops on the
discs of leaves, or, more commonly, by immersing them in the solutions;
and sometimes by both methods. A summary of the results, with some
concluding remarks, will then be given. The action of various acids
will afterwards be described.
COLUMN 1 : SALTS CAUSING INFLECTION. COLUMN 2 : SALTS NOT CAUSING
INFLECTION.
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