26 
Colorado Experiment Station 
and will expand in the direction of least resistance. This causes 
the tuber to grow irregular and rough. It is easier to maintain the 
type in loose and open soils where the tuber can expand without 
unequal pressure from the soil. Ill-shaped or knotty tubers gen¬ 
erally occur when the growth of the tuber is checked, usually on 
account of lack of water, and then starts the second time, the knobs 
representing the second growth. From this, it will be seen that 
it is necessary to keep the soil conditions such that the tuber can 
continue a normal df^velopnient without check. 
SEED CERTIFICATION 
With the development of the potato-growing industry in this 
State, some provisions are necessary to secure the purchaser of 
seed potatoes against an inferior product. To obtain this condi¬ 
tion a system of seed certification is necessary. It is true that 
here and there are seed producers who make a specialty of pro¬ 
ducing high-grade potatoes from which the average grower may 
obtain high-class seed. But these seed growers are few and far 
between, and as the welfare of an industry depends upon the in¬ 
telligence and standards of the average grower, it is necess'ary 
that the largest possible number of them should have access to 
high-grade seed. 
A system of seed certification by properly qualified officials 
who can certify to the quality of the seed is necessary. This 
would tend to raise the general standard of the product, and also 
furnish an incentive to many growers to produce certified seed. 
A system of certification was formulated by the Colorado State 
Potato Growers’ Association and incorporated in its constitution 
and l^y-laws. This certification calls for two inspections of the 
growing field during the summer, and a bin inspection after the 
harvest. In the field inspection, special attention is paid to the 
health and vigor of the plants, the absence or presence of disease, 
the fullness of the stand and the uniformity of the plants in the 
field. The two field inspections should be made at intervals of 
four to six weeks. The last inspection should be made as late 
as possible before the harvest, so as to detect the most dangerous 
diseases. 
The bin inspection gives the inspector an opportunity to 
determine the trueness to type of the variety grown, the freedom 
from scab and the general quality of the tubers. If after inspec¬ 
tion, the inspector finds that the product measures up to the 
standard, a certificate to this effect is granted to the grower. This 
certificate states the variety, the results of the inspection, and in 
fact all possible informaGon connected with the potatoes. The 
grower may then use his certificate in advertising his product 
