8 
should know accurately how much earliness is dependent 
upon the color of our soil, and also the corresponding in- 
fluence of color upon the amount of evaporation which 
takes place from the soil. 
The question of the influence of sunlight upon plant 
growth and development is a very important one. Without 
these records we can scarcely suggest an explanation of 
why periods of maturity should vary in different years, or 
as between different plantings during the same season. 
We have already shown that the units of temperature 
alone during the period between vegetation and maturity 
are not sufticient to furnish a,solution of this problem, and 
we have received clues which suggest that one of the want- 
ing factors is the recording of the sunlight. From these 
reflections it will be at once seen that one of the greatest 
needs of agriculture is a careful and extended study of the 
soil and those soil conditions which come under the head, 
directly or indirectly, of meteorology. With this question 
is also involved the chemical considerations concerning 
what may be called chemical reactions within the soil, as 
nitrogen in its agricultural form finds ready escape from 
the land through the drainage, and it would at first thought 
be supposed that the amount of nitrogen would be greater — 
in the lower than in the upper layers of the soil. Observa- 
tions, however, show that the upper soil is richer in this 
element than the lower portion of the soil. This undoubt- 
edly comes in part from the action of capillarity, whereby 
the nitrates carried down by the rain are brought to the — 
surface again through evaporation, which is continually 
taking place and drawing water and its soluble ingredients 
from below upwards. In the summer-rainless regions of 
the west this capillary action finds expression which is re- 
cognized in the truly alkali lands, the soluble alkalies being 
brought to the surface in excess and deposited there in a 
crystalline form, thus destroying the value of the land for 
agricultural purposes. | 
Each portion of a plant seems to have a temperature at 
which its functions are best performed. We have stated 
in a previous report that maize seed will germinate at or — 
about 41 degrees F., but the growth at this temperature is 
very slow. If the growing plant has its roots exposed to a — 
temperature of about 60 degrees F., wilting will occasion- 
ally take place. This seems to come from the fact that 
the function of the roots to absorb, water cannot be per- 
formed at this temperature sufficient to furnish the water 
lost through evaporation from the leaves. A similar action 
may often be observed during the warmest and driest por- | 
tion of the summer, when the roots fail to supply the 
amount of moisture. thrown off by the leaves, and hence — 

