PASSAGE OF WATER THROUGH THE PLANT 119 
giving off a great deal of water the stomata are more widely 
open than when little is being given off. 
By means of the next experiment some idea of the rate 
at which water travels | 
through the plant is ob- 
tained. 
| Take a glass 
vessel with 
rubber stopper with two 
holes ; into one fix a laurel 
shoot, into the other a 
bent tube with a gradu- 
ated scale attached. Fill 
the vessel and bent tube 
quite full with water. 
It will be 
found that the 
water moves along the 
bent tube. 
Experiment. 
Result. 

‘Water is | 
Conclusion. Fic. 140.—APPARATUS SHOWING RATE 
being gradu- OF ABSORPTION OF WATER. 
ally absorbed by the shoot. | 
Now, if the amount of water between two successive gradua- 
tions in the scale is known, the rate of absorption may be 
calculated. Thus, if the amount of water between two gradua- 
tions is 4, cubic centimetre, and if the water in the bent tube 
passes through six graduations in one hour, it is clear that 
i; cubic centimetre of water have been absorbed by the 
plant in the given time. . 
The rate of absorption, as said above, varies. 
tien oF Lastly, it must be noted that, although plants 
Waterfrom do for the most part take in water through the 
Atmosphere. oi], there are certain plants, especially in dry 
countries, where there may not be even a slight shower for 
months, which take in water from the atmosphere. This is 
the case in plants with aerial roots (Chapter II). 
