i8 QUEEN'S QUARTERLY. 



living plants contain a very considerable proportion of water in their 

 tissues. In seeds this proportion may be as low as about ten j 

 cent., while in vegetables and fruits it is often above nine y P^r cen . 

 The necessity for this water is clear when we note its duties, i'.rst, 

 protoplasm can be alive only when it contains some water, beecis are 

 among the dryest of living vegetable substances, but they normally 

 contain between ten and twenty per cent, of water, and this is an 

 indispensable condition of their continued life. Wlnle dry, the life 

 processes in seeds are very slight and difficult to detect, but the pres- 

 ence of additional water with a suitable temperature will result in 

 greatly increased activity, and the seedling as it develops demands 

 an increasingly great supply of water. Protoplasm that is growing 

 is semi-fluid, and its activity is directly dependent on the maintenance 

 of an adequate water supply. Another purpose served by water is 

 the transportation of food materials into and ^through the plant, as it 

 is quite certain that all the raw materials for plant food enter the 

 cells as solutions in water. 



Admitting the necessity for water, we recognize that the prob- 

 lems confronting the plant are: first, the securing of an adequate 

 supply, and, second, the conservation of this supply. 



Since water enters land plants by way of the roots alone, the 

 extension of the root system to tap large areas of soil is the ordinary 

 reply of root protoplasm to the stimulus of an insufficient quantity 

 of water. This extension takes the form of repeated branching as 

 well as of lengthening of root axes, and each branch and rootlet is 

 again increased in surface by the production of innumerable root 

 hairs. Thus the soil is thoroughly searched, and forced to yield 

 whatever water may adhere to its particles. In soil containing free 

 water which may be drained away, we find greatly restricted root 

 systems, and a very slight production of root hairs. 



Turning to the problem of water conservation, we find the con- 

 ditions so various that they have stimulated a wide variety of ex- 

 pedients. Drouth may be periodic or continuous, excessive or slight. 

 Again the periods may vary in intensity and length, from an abso- 

 lutely rainless season of several months to the few intensely warm 

 hours of a summei day. It should be noted here that lack of water 

 within the plant may be due to either an insufficient income or to an 

 excessive outgo, or to both combined. The dryness of the atmo- 

 sphere on clear cold days, together with the fact that the soil water 

 is to a great extent locked up by frost, make our Canadian winter a 



