Transpiration as a Factor in Crop Production. 141 
that water evaporates less freely from a partially saturated object 
than from one fully saturated. A slight wilting also occurred, 
in a few instances. This may actually reduce transpiration by 
stomatic closure due to a physical collapse of the tissues rather 
than thru regulative closure. 
An examination of stomata in wilted leaves has shown them 
to be practically closed as compared with open stomata in a 
turgid leaf at the same time. 
Future studies may throw more definite light upon these 
speculative observations. 
EFFECT OF AN OVERABUNDANCE OF SOIL MOISTURE. 
(THREE-YEAR AVERAGE.) 
An overabundance of soil moisture, existing in an average 
relative saturation of 97 per cent, decreased the moisture-free 
weight of stalk 11.3 per cent, the weight of ear 21.1 per cent, the 
weight of leaves 14.4 per cent, the total dry matter 16.7 per cent, 
the total water transpired 9.8 per cent, and the total leaf -area 
9.1 per cent. The water used per gram dry weight of ear was 
increased 13.5 per cent, per gram total dry matter 8.2 per cent. 
The water used per unit leaf-area was reduced 1.1 per cent. 
The ratio of leaf -area to dry matter was 9.4 per cent greater, and 
the ratio of ear weight to stalk weight 11.2 per cent lower. The 
average height of plant was nearly normal, being reduced 2.8 
per cent, or 3 inches. 
From such data as these, showing an increase in the water 
requirement per unit weight of dry matter, investigators have 
rather generally concluded that the plant in some way releases a 
control over the transpiration rate, and that the plant strives 
to get rid of the surplus water by increased transpiration. It has 
been frequently said that less work is required by the plant to 
absorb moisture from a saturated soil, and that it is therefore 
used more extravagantly. The writer, however, believes that no 
consideration of a vital element on the part of the plant need 
enter into an interpretation. It appears more probable that the 
water requirement per unit dry matter is increased because 
of a reduction in the available fertility due to surplus water in 
the soil. Toward the end of the season the lower leaves of the 
plants usually show symptoms of a lack of nitrogen. An average 
reduction of 16.7 per cent in the dry weight of the plant supports 
this interpretation. 
