PLANT-AUTOGRAPHS—BOSE. 441 
spontaneous movements (fig. 18). But a fresh accession of stimulus 
from outside renews these pulsations. 
In the matter of these so-called spontaneous activities of the 
plant I find that there are two distinct types. In one the overflow 
is initiated with very little storage, but here the unusual display of 
activity soon comes to a stop. To maintain such specimens in the 
rhythmic condition, constant stimulation from outside is necessary. 
Plants of this type are extremely dependent on outside influences, 
and when such sources of stimulus are removed they speedily come 
to an inglorious stop. Averrhoa is an example of this kind. In 
the second type of automatic plant activity I find that long-continued 
storage is re- 
quired before an 
overflow can be- 
ein. But in this 
case the sponta- 
neous outburst is 
persistent and of 
long duration, 
even when the Fia. 18.—Gradual stoppage of pulsation in an isolateq Desmodium leaflet 
plant is deprived - due to rundown of stored energy. 
of any immediately exciting cause. These, therefore, are not so 
obviously dependent as the others on the sunshine of the world. 
Our telegraph plant, Desmodium, is an example of this. 
INSTANTANEOUS RECORD OF GROWTH. 
As a further example of automatic activity we may take the 
phenomenon of growth. The rate of growth is so extremely slow 
that even the proverbial pace of the snail is two thousand times 
quicker. It would take an average plant 200 years to cover the 
short distance of a mile. This extreme slowness is a serious draw- 
back in the investigation on growth. For even with the existing 
magnifying growth recorders it would take many hours for the varia- 
tion of growth to be recorded under the given changed conditions 
in the environment. The results thus obtained are subject to errors 
brought about by the variation of growth which takes place spon- 
taneously in the course of a few hours. Growth can be assumed to 
remain constant only for a short time; on this account it is necessary 
to conclude an experiment in the course of a few minutes. 
By means of microscopic projection it is possible to magnify 
growth; but such an arrangement will not be self-recording. ‘Fhere 
is again a serious error introduced by the action of strong light, 
which profoundly modifies the rate of normal growth. 
These difficulties have been overcome in my high magnification 
crescograph, which records the absolute rate of growth in a time so 
