Lie 
in the following table, where the figures represent the sums of sun- 
shine temperatures necessary to complete the growth from germi- 
nation to harvest. 
Sunshine Sunshine 
Plant. temper- Plant. temper- 
ature. ature. 
iG: o1G: 
Wisrerianuwhea tes t=. 2-0-2 4--.-1- 222-8 2,462 || Normandy barley.-.-...-.----.-------- 1,810 
iINormandy wheat.-----.-/-.2.-.--'5.-- 2330) || Normandy beans22.------2-s-------_-2 2,210 
INormandyOats £5 228k. .--2oe<ss5e-e2 2,197 || Normandy buckwheat..-.-..--------- 1,579 
@ 
Marié-Davy (1881), in his chapter on the influence of heat on the 
time required for vegetation, adopts the principle enunciated by 
Boussingault, of the equality of the sum total of the temperatures, 
but thinks that the temperature required to bring a plant to the 
flowering stage is the sum of the mean darly temperatures in the full 
sunshine, and not the temperature of the air in the shade.* According 
to his view, the heat is needed in the soil in the early part of the 
growth of the plant; but after the flower is formed, or during the 
process of perfecting the fruit, sunlight is needed, and during this 
stage he uses the actinometric degrees of the Arago-Davy actinometer 
as an index of the progress of the plant. I have, therefore, in the fol- 
lowing table collated the figures given by him for wheat. The third 
column gives the sum total of the mean daily shade temperatures, 
counted from February 1 of each year up to the date at which the 
total amounts to 1,264° C., or within half a day thereof, that being 
the adopted shade constant for the flowering of wheat that was sown 
on or about the 21st of March. The fourth and fifth columns give 
the dates and sum totals of temperatures observed with a naked-bulb 
thermometer on the grass in the full sunshine, assuming 1,569" C. 
as the thermal constant for this thermometer. The sixth column 
gives the observed dates of flowering. As these dates agree with those 
in the fourth column better than with those in the second column, 
Marié-Davy considers them as confirming him in the use of the 
unprotected solar thermometer. In order to bring out the total effect 
of sunlight and sun heat Marié-Davy has computed the sum total of 
actinometric degrees from February 1 up to the dates given in column 
2 and in column 4, respectively. These results are given in columns 
7 and 8, which show that 1878 was a very precocious year, as com- 
pared with the others, in that the date of flowering was very early, 
but the sum total of its actinometric degrees was very small and its 
erops were very poor. 1879 and 1877 show larger actinometric sums, 
but the largest sums are given by the years 1873, 1874, 1875, and 1876, 
which were also very excellent crop years. 
2667—05 mM——12 
