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446 REPORT OF THE HorRTICULTURAL DEPARTMENT OF THE 
sum total of heat up to that date; this sum total is the amount of 
heat required by the plant to reach the epoch in question. 
It is probable that in our climate where temperature, of all the 
attributes of climate, pre-eminently influences vegetation, Hoff- 
man’s thermal constants can be used with some accuracy but only 
after long-continued observations in the locality in which they are 
to be used; for, beyond all question, plants will accommodate them- 
selves to different sum totals of heat for their several life events in 
different localities. 
If we seek for a more concrete guide than the thermal constant 
for forecasting the advent of blooming-time, we shall find even less 
satisfaction. The retreat of winter and the coming of spring are 
marked by the disappearance of snow, the breaking up of ice, the 
appearance of animals, the migration of birds and the putting- 
forth of vegetation. But all of these fail as reliable heralds of 
blooning-time. If we turn to the weather we shall find but little 
that is tangible, nothing that will guide predictions for more than 
a few days in advance. Blooming-time seems to follow a some- 
what complicated series of weather changes, the chief features of 
which are a succession of hot and cold waves, the latter diminish- 
ing in frequency and force until the total amount of temperature 
for the season seems to force out the blossoms. 
The physical features of a location have a marked effect on the 
blooming-time quite aside from the altitude and latitude which for 
most part govern temperature. Among the minor factors are 
proximity to large bodies of water; the slope of the land; the 
character of the soil; winds and wind-breaks. Plants bloom earlier 
in a sheltered valley, on a southern slope, or on a warm sandy 
soil, than on exposed plateaus, bleak hillsides, or heavy cold soils. 
The color of the wood, whether dark or light, may have a slight 
influence on the time of blooming. 
With these brief considerations we pass to a discussion of the 
blooming dates of the apple, pear, peach, plum, cherry, apricot, 
nectarine and grape at this Station. Blooming dates are given 
for six years, from 1902 to 1907 inclusive for the tree fruits, and 
for the years 1892 to 1898 for the grape. For many years this 
Station has kept records of the blooming-time of the fruits grown. 
In 1902 an arrangement was made whereby such records were to 
be kept by the U. S. Department of Agriculture for the joint use 
of the Station and Department. The dates here given were taken: 
for the first five years by H. P. Gould and the last year by W. F. 
Fletcher, both of the Department of Agriculture. 
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