216 HOW CROPS FEED. 
bled rye to yield a maximum of grain and brought wheat 
and oats very closely to a maximum crop. Hellriegel no- 
ticed that the p'ants exhibited no visible symptoms of 
deficiency of water, except through stunted growth, in 
any of these experiments. Wilting never took place ex- 
sept when the supply of water was less than 2"|, per cent. 
Grouven (Ueber den Zusammenhang zwischen Wit- 
terung, Boden und Diingung in threm Hinflusse auf die 
Quantitat und Qualitét der Erndten, Glogau, 1868) gives 
the results of an extensive series of field trials, in which, 
among other circumstances, the influence of water upon 
the crops was observed. His discussion of the subject is 
too detailed to reproduce in this treatise, but the great 
influence of the supply of water (by rain, ete.,) 1s most 
strikingly brought out. The experimental fields were 
situated in various parts of Germany and Austria, and 
were cultivated with sugar beets in 1862, under the same 
fertilizing applications, as regards both kind and quantity. 
Of 14 trials in which records of the rain-fall were kept, 
the 8 best crops received from the time of sowing, May 
Ist, to that of harvesting, Oct. 15th, an average quantity 
of rain equal to 140 Paris lines in depth. The 6 poorest 
crops received in the same time on the average but 115 
lines. During the most critical period of growth, viz., 
between the 20th of June and the 10th of September, the 
8 best crops enjoyed an average rain-fall of 90.7 lines, 
while the 6 poorest received but 57.7 lines. 
Tt is a well recognized fact that next to temperature, 
the water supply is the most influential factor in the prod- 
uct of acrop. Poor soils give good crops in seasons of 
plentiful and well-distributed rain or when skillfully irri- 
gated, but insufficient moisture in the soil is an evil that 
no supplies of plant-food can neutralize. 
The Functions of Water in the Nourishment of 
Vegetation, so far as we know them, are of two kinds 
