THE VEGETATIVE FUNCTIONS OF PLANTS 
serve more of the water taken in than do other species. 
The two extremes in this respect are desert plants, such 
as cacti, sage-brush, and euphorbias, and water-loving 
plants, such as water-lilies, ferns, touch-me-not or jewel- 
weed, and cucurbits like pumpkin and squash. A con- 
venient method of measuring these differences is to com- 
pare the weight of water absorbed with the weight of 
dry matter produced. This ratio is known as the relative 
water requirement of the plant. Thus, if a given plant, 
during its growth, has taken in 100 pounds of water, and 
the solid matter produced, when dried out to a constant 
weight in a drying oven, weighs 2 pounds, the relative 
water requirement is (100 : 2) 50. 
44. Government Experiments. In experiments con- 
ducted for the United States Department of Agriculture, 
for the purpose of ascertaining the relative water require- 
ments of various plants, it was found that the weight of 
water taken in by hubbard squash plants amounted in 
some cases to over 6,000 times the weight of the fruit, 
and to over 900 times the weight of the total dry substance, 
not including the roots. Other ratios, in round numbers, 
were ascertained, as follows: 
TABLE I. WATER REQUIREMENTS OF PLANTS 
Plant 
Water requirement based on 
Grain 
Dry matter 
Rye. . . 
1, 800 
496 
744 
900 
8 9 I 
7S 
300 
Rice 
Flax 
2,800 
1, 600 
6,400 
Cucumber 
Sunflower 
