28 
total darkness, is probably = to causes similar to those producing the 
st movement of the leaflet 
n, plants grown and ‘laminated only by ^u rays of low 
arkness i 
orgaus, the plant as far as this kind of light is concerned is in darkness. 
n the other hand red and yellow rays pass unhindered to the plant, 
its leaves can continue the nmm qnin of starch without inter- 
Féféliaó; so that the duration of an experiment may be prolonged without 
so complete an overthrow of the normal Ve Ae: as obtains when 
the plant is grown in total darkness. Under these conditions the leaves 
in the highest position which it was mecha ssible to attain. 
On removing the coloured solution from around the plant a striking 
thing happene In the course of two hours all the leaves moved 
down through an angle of 40? to 60°. The action of pure diffuse light 
in this case was the greater from the fact ei that the plant had 
been so long protected from the blue and violet rays. 
Finally it must not be supposed that the "upra and downward 
movements of a leaf rachis occur in the same vertical plane. Asa 
matter of fact the leaf points sometimes to y right sometimes to left of 
the positions in which it is at its extreme elevation or depression. 
Roughly speaking the apex of a leaf axis traces an ellipse in performing 
one diurnal oscillation, and its extreme /ateral fluctuation may reach as 
much as 20? or 25? of arc. 
I have dealt in some little detail with these rachis movements, since 
it is to these that Mr. N owack attaches s d wol doni 
down movements not dissimilar in nature to those shown Dy certai 
other Leguminous liii? that the most marked of these movements is is 
and that the regularity of these movements is directly affected 
variations in illumination and in temperature. I contend that the ex- 
planation of these movements, as also of those of the leaflets, is to be 
influences as light, temperature, and relative humidity combined with | 
individual peculiarities, rather than in — — such as” 
those held by Mr. Nowack. 
The earthquake and schlagwetter positions of rachis are shown 
various ine not infrequently. Six or eight leaves on a single plant 
may be in one or other of the positions at once. . Nowack n 
longer des ds them as foretelling n — either an earthquake or a 
mine "impres wt sudden changes of barometric pressure at the spots 
indicated. ase of the earthquake palin, he regards the prophesy 
fulfilled if pre ae dapes of a certain number of days after the bending 
reaches a maximum a e rey from low e high barometric. 
pressure takes place. milarly regards schlagwetter, except. that 
the c — is eqn high » low iei 
In words, these positions indicate the sudden development of 
well-marked high or low pressure centres — in the directions 
