EXPERIMENTS IN CULTIVATION OF POTATOS. 127 
ounces or over. ' Factor ' was used in this series, the seed tubers 
being taken from the same stock as those used in the first three series of 
experiments. The distance apart was the same as in the foregoing, 
and twenty tubers were planted in a row. There were three groups, 
in one the seed tubers weighed approximately one ounce each, in the 
second two ounces, and in the third three ounces, and each group was 
repeated four times, so that eighty seed tubers of each kind were planted. 
The planting was done in mid-April, and the plants were lifted and 
weighed on September 3 after they had died down. 
Size of Tub«r. 
Yield. 
Ware and Seed. 
Chats. 
Total. 
1. Small, about ioz. . 
2. Medium, about 2 oz. 
3. Larger, about 3 oz. 
lb. oz. 
M5 14 
175 IO 
183 8 
lb. oz. 
5 1 
5 0 
5 6 
lb. oz. 
I50 15 
180 10 
188 14 
The yield of the medium and larger tubers, of about the size 
usually regarded as " seed size," was markedly greater than that of 
the small tubers, and the chats were somewhat less in proportion to 
the yield. A striking thing, however, which is not brought out in 
the table, but which is evident on* comparison of the weights of the 
individual plant-yields, is the tendency of the small tubers to produce 
a great proportion of plants giving only a small yield and a 
small proportion only giving a larger yield than the average. The 
contrast in this direction with the yield of those of a larger size is very 
marked. 
V. Effect of Spacing on Yield. 
An endeavour was made to ascertain the effect of the amount of 
space available for the development of the individual plant upon the 
yield both of the individual and of equal plots of land occupied by 
the differently spaced plants. The variety ' Arran Chief ' was used in 
this experiment, the seed having been grown at Wisley in 1916. As 
usual, the seed was sprouted before planting. The crop was lifted after 
the plants died down in September 1917. The results are shown in the 
folio wing table, where each space represents an area of one square rod ; 
the top line in each space shows the distance apart of the rows and the 
plants in the rows on the plot in inches, and the area occupied by each 
plant in square feet ; the first row of figures shows the yield of ware and 
seed, the second the weight of chats, and the third the total yield from 
a plot of one square rod ; and the last line shows the average weight 
of produce from each root. The exposure of all the plants on each 
plot was the same ; failures in the rows have been allowed for in 
arriving at the totals and averages, and the totals given are averages 
of duplicate series. 
