136 Proceedings of the Royal Society of Edinburgh. [Sess. 
(5) Potatoes planted on February 1 had developed long shoots by February 
28, and were showing in the surface by March 22. Others planted in 
the open on the same date showed no signs of life by March 22, and 
even the shoots they had on them at the time of planting had died and 
rotted by that date. 
VIII. Conclusions. 
By both covering the earth with a layer of ashes and putting a shelter 
over it, I have on one occasion kept the soil 10° F. warmer than in the open. 
Even so, I have not surpassed Nature in this respect, for we have seen that 
under a cover of grass and moss the temperature of the soil was 10° F. 
higher than open soil. On the banks of ditches, under the lee of hedgerows, 
and in the woods, protected from the wind and from the effects of radiation 
by a covering of fallen leaves, grass, and moss, the roots of spring flowers 
lie untouched by frost the whole winter through. A spell of warm rain as 
early in the winter as December will add just that necessary warmth to 
the soil to make them put forth their leaves, and we find them in flower 
when as likely as not winter has returned with all its rigour. 
Encouraged by the mild weather of December 1918, a single primrose 
had forced its way through the mossy turf I have had under observation, 
and on February 10, 1919, was in flower — its leaves and flowers in an air 
temperature of 15° F., its roots at 33° F., a difference of 18‘0° F. Snow 
and cold rain in January and February have deterred its companions, and 
it stands there alone still — as it were a vision of a spring that might 
have been. 
As far as wild spring flowers are concerned, I believe the temperature 
of the air plays but a very secondary part to the underground temperature 
in determining an early or late spring. 
(Issued separately August 5, 1919.) 
