GROWTH 137 
(yellow), the other a solution of copper sulphate (blue). ‘The 
difference in the two should be carefully noticed. 
Cover up a plant of Wood Sorrel (Oxalis) 
pee: 7 ander.a belly jar. 
During the day the three leaflets are spread 
cee out; as evening approaches they close up. 
Some plants are affected by alternation of 
Conclusion. 
day and night. These sleep movements, as 
they are called, are very well seen in Mimosa (Sensitive plant). 
It is most fascinating to watch the Mimosa bushes im a garden 
hedge closing up as evening approaches, as can be done in 
the tropics, where Mimosa is a common outdoor plant. 
During the day the delicate leaves spread out ; at sunset thev 
fold up, so that not a blade is visible. 
Attach a young Bean seedling to the cork of 
a bottle with water in the bottom, in such a 
way that the radicle points upwards. 3 
The radicle will curve round so as to grow 
_ towards the centre of the earth. 
The radicle is affected by gravity in such a 
way that the tip grows towards the centre 
Experiment D. 
Result. - 
Conclusion. 
of the earth. 
It would be interesting to know why the radicle should 
be affected by gravity when the lateral branches of the root 
are not. At present it is only possible to state the facts. 
Grow seedlings of Mustard in a sieve con- 
taining damp sawdust. 
The roots will grow downwards vertically in 
the sawdust, then when they make their way 
through the holes of the sieve, they will cease to grow verti- 
cally, but will curve towards the sieve. 
Moisture attracts roots more powerfully even 
than gravity. 
_ Experiments show that growth is most active at a tempera- 
ture of 37° C., that is to say, the temperature of the human 
body. Too low a temperature, such as freezing-point, kills ; 
a late spring, as everyone knows, destroys early blossoms. 
Experiment E. 
Result. 
Conclusion. 
