his plants on which his
own life and the world's depend and, even realised something of its
vicissitudes, so the vegetable physiologist has here one of the many
problems of his science. The invention of growth-measuring instruments
has thus been one of his main endeavours. He has hitherto succeeded by
the use of levers with unequal arms to obtain a magnification of about
20 times, and even then it takes many hours for growth to become
perceptible; owing to the practical impossibility of maintaining the
external conditions constant for so many hours, the results of
measurement of growth become vitiated. It is therefore necessary to
produce a magnification so high that growth should become measurable in
less than a minute. The first improvement effected by the lecturer, now
some fourteen years ago, was his Optical Lever, which at once raised the
magnification from 20 to 1000 times, an advance which at the time seemed
to many incredible, but it is at length coming into use in advanced
laboratories in Europe.

THE RECORDING CRESCOGRAPH

A new apparatus devised by the lecturer, the Recording Crescograph, is
described in the Transactions of the Royal Society, and of the Bose
Institute. By a compound system of levers the magnification is raised to
10,000 but this is not without great technical difficulties, which cost
five years of efforts to overcome. Thus the levers require to be
extremely light; this was secured by the use of an alloy of aluminium
used in the construction of Zeppelins: this combines lightness with
rigidity. Another difficulty almost unsuperable arises from the friction
at the bearings of the fulcrum, the best watch jewels made of ruby were
employed, but the supply was cut off from Germany by the war. This
proved a blessing in disguise, for it forced the lecturer to devise a
new principle of suspension using local material. This was found in
practice to be far superior to jewel bearings, which became clogged by
invisible dust particles present in the air. With this Recording
Crescograph many phenomena of extreme interest have been discovered. The
plant itself not only recorded its normal rate of growth but the
slightest change induced in it by the action of different forces. So
delicate was the apparatus that it analysed growth into a series of
pulses, a sudden shooting out followed by a partial recoil. It showed
how the growth of the plant was retarded by a mere touch, and the time
it took the plant to