Page:Life Movements in Plants.djvu/223

Rh the leaf of Minwsa and the movement due to growth, which is summarized as follows :—

(1) An increaseor positive vm'iation of [my/or in- duces an, erection or positive 'response of the leaf of Mimosa, and (1; positive variation 01‘ (mhancement of the rate of growth.

(2)11 diminution or negative mtriuiimi of larger induces a, fall or negative response of the leaf of Mimosa, and a negative variation or retarda- tion of the rate of growth.

Experiment 73.——-The recording lovers are at ﬁrst so balanced that very little tension is exerted on the plant. Record of normal growth is taken of a specimen of (Irinmn. The tension is gradually increased from one grain to ten grams. The table given above shows how growth—rate in- creases with the tension till a limit is reached, after which there is a retardation.

I Tension. Rate of growth.

‘1 0 (Normal) ...i Q41 ,1, per second.

1 4 grams  0'44 [L n n

! 6 ,,   048 ., .,

i 8 H coo cc. .00! H N

no ,,   0-40 .L .. .,

Increase of turgor induced by irrigation enhances the rate of growth. Irrigation with warm water induces a further augmentation of the rate of growth.