SOME LESSONS IN BOTANY 53 
Large quantity of water required. —It may occur to the 
reader that this could not make a very rich diet for the plant, 
for at best the solution is very thin and weak. That is the 
truth; and, therefore, the amount of water that must be 
taken up to meet the needs of the growing plant is very large. 
It has been learned that 338 tons of water are absorbed by 
the roots of spring wheat to produce one ton of dry matter 
in the ripe plant, while growing oats require even more mois- 
ture. In other words, leaving the stubble and roots out of 
the account, a wagon load of grain bundles weighing a ton 
represents about 338 tanks of soil water, each weighing a 
ton. This water or sap is carried up into the leaves, where a 
small part of it, together with the dissolved materials, is 
used for the growth of the plant, and the rest of the water 
escapes into the air. There are very few parts of the world 
where rain falls in such abundance throughout the growing 
season (and yet never too much) as to enable a rich soil to 
produce the largest crop it is capable of producing. This 
ideal may be practically realized, however, by means of a 
good irrigation system; and it is easy to understand why 
irrigated land usually produces such heavy crops. 
The soil must not be too wet. — Notwithstanding the large 
demands of plants for water, very few of them will thrive 
if the soil is excessively wet. It should be merely moist. 
This is most frequently shown in the spring of the year when 
yellow patches appear in wheat, corn, and flax fields. These 
are caused by the presence of too much water and too little 
air in the soil. In some sections of the country where crops 
suffer much from this cause, farmers go to a great deal of 
expense to put in a good drainage system for their land. 
3. Roots used for storage of food. — Another use which the 
plant makes of its roots is to store food in them for future 
