No. 98.] 67 
and one plat was covered with four, the other with six inches of coarse 
sand. On May 8, dug into the hills and found sprouting had com- 
menced; the temperature of the soil under the four inches of sand 
being 54°, under the six inches of sand, 52°. Vegetation occurred 
upon both plats upon May 22. During the summer a number of hills 
were destroyed by digging, in order to study progress, and on June 12 
we noted that the potatoes under four inches of sand were rather more 
forward than those under six inches of sand, and were very prolific ; 
those under the six inches of sand more prolific than any other plat 
noted. On June 27 the potatoes under six inches of sand in bloom, 
and on August 24 some cooked were pronounced of superior quality. 
September 1, removed from two plants ten very large tubers; there 
were no small ones. September 21, dug these potatoes and found 
twelve hills covered with six inches of sand yielded twenty-two and 
one-quarter pounds merchantable, and one-quarter ounce small pota- 
toes; the eighteen hills under four inches of sand yielded thirty-three 
pounds merchantable, and one pound of small potatoes. 
The full significance of this yield can be best understood by giving 
in tabular form the yields of the nearest plat cultivated in the ordinary 
way, and all calculated to twelve hills : 
egy: Merch. tubers. Small tubers. 
12 hills covered with six inches sand. 22 1-4 lbs. 1-4 oz. 
12 hills covered with fourinches sand. 22 lbs. 10 2-3 ozs. 
Perdis, LIC CeLCULUTS (4 ew ereiein mene 9 1-4 lbs. 3-4 02. 
PE ACKOL CULE. noo cub, bie ereyes + 93-4 lbs. 1 lb. 11 ozs. 
We shall return to these figures in a few paragraphs, in order to 
show their bearing upon a hypothesis we have formulated, as follows: 
For the best growth of the potato, we require to keep the tubers warm 
and dry; the roots moist and cool. To give a practical test to this 
theory we arranged the following experiment : 
On April 24 we threw up some high ridges, four feet apart, and 
planted ordinary cuts, one foot apart on the ridge. These vegetated 
May 22. On June 7 we applied a mulching of four inches of moist 
straw between the ridges. ‘The idea being that by high ridging we se- 
cured dryness for the tuber, by mulching the intervals we secured: 
moisture and coolness for the roots. There was no hoeing or culti- 
vation during growth, the weeds being simply cut away lightly with 
the hoe, so as to disturb the soil as little as possible. The yield of the 
150 hills was 138 1-2 pounds of merchantable tuber, and 33 3-4 pounds 
of unmerchantable. 
In this, and the preceding experiment with sand and straw, we have 
parallel series designed to embrace the points which shall open up to 
us some of the laws which regulate productiveness in the potato. In 
the straw, coolness and dampness during a portion of the growth; in 
the sand and in the mulched intervals, heat and dryness for the tuber, 
moisture and coolness for the roots. Let us bring together the results 
calculated to the 100 hills: 
