2. An increase in the size of the seed from one eye to half a potato produces an increase in the net value of the crop.

A comparison of the half potato with the two eyes shows that:

1. For the total yield (large and small) of 95 experiments, 76 are in favor of the half potato and 19 in favor of two eyes.

2. For marketable yield (total less small) of 73 experiments, 58 are in favor of the half potato and 15 in favor of the two eyes.

3. For net marketable yield (marketable less amount of seed) of 30 experiments, 23 are in favor of the half potato and 7 in favor of the two eyes.

4. For net value of crop (value of crop less value of seed) of 30 experiments, 22 are in favor of the half potato and 8 in favor of two eyes.

A comparison of the whole potato with the half potato shows that:

1. For the total yield (large and small) of 54 experiments, 46 were in favor of the whole potato and 8 in favor of the half potato.

2. For the marketable yield (total less small) of 42 experiments, 36 were in favor of the whole potato and 6 in favor of the half potato.

3. For the net marketable yield (marketable less amount of seed) of 13 experiments, 7 are in favor of the whole potato and 6 in favor of the half potato.

4. For the net value of crop (value of marketable less value of seed planted) of 12 experiments, 7 are in favor of the whole potato and 5 in favor of the half potato.

The Value of Bud and Stem Ends and the Middle of the Tuber for Seed.-Many ideas have prevailed as to the relative values of different parts of the tuber for seed. Some growers advocate the removal of one end or the other, but thus far the experiments conducted at a dozen stations, including such varying points as Illinois,' New Jersey,' and North Dakota Experiment Stations, show that there is no material difference noticable in yield that could be attributed to the different pieces, and that the two ends of a tuber are practically of equal value.

Viability. The buds of tubers vary considerably in their ability to grow, and the same is true of the tubers themselves. Goff, of Wisconsin, when using the variety Burbank, obtained a stand varying from 88 to 100 per cent. of the potatoes planted. The importance of proper moisture content of the soil is shown by the results reported in the following table by Woods, of Maine:"

1 Ill. Bul. 40, p. 132. 2 N. J. Report, 1898, p. 308. N. D. Report, 1901,

pp. 40-42.

4 Wis. Report, 1897, p. 306.

Me. Bul. 98, p. 183.

This poor stand was largely due to a very dry spell in May and June, and the differences observed in the various varieties may be due to the vitality of the varieties themselves, or to the way in which they were grown and stored, or to both causes. Girard, of France, summarized his experiments some time ago, showing the influence of the size of the tuber upon the "stand "' and yield.

The yield of No. 2 is not comparable with the others, because the same weight of seed was not used. Plats 1 and 3 are probably the best to use for ordinary consideration, and would show that from 90 to 95 per cent. of the tubers planted should grow, but it is a well-known observation that under adverse conditions -as, a dry season, ill-fitted land, etc.-a small cutting is not so likely to grow as a whole tuber.

The diagram (Fig. 16) shows that with Carman No. 3, where twenty plats were noted, there were 3 chances in 20 that the germination of the tubers and stand would be 100 per cent., and that it is much more likely to be between 91 and 98 per cent. than any other

3

2

1

100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 77 76 75

FIG. 16-DIAGRAM SHOWING STAND OF TWENTY PLATS OF CARMAN NO. 3 POTATOES1

The percentage stand is shown on the base-line. The hight of the curve from the base-line shows the actual number of plats.

FIG. 17-DIAGRAM SHOWING STAND OF THIRTY-SIX PLATS OF EARLY TRUMBULL POTATOES

1

The percentage stand is shown on the base-line. The hight of the curve from the base-line shows the actual number of plats.

number, although the average as usually worked out would show 93.5 per cent.

With Early Trumbull, using seed showing the rosette disease (Rhizoctonia solani) and some not showing it, treated with various fungicides, the average germina

1 From data in Ohio Bul. 145, P. 21.

ting power for 36 plats is 73.8 per cent. Yet, here again this does not convey a true impression, as on six plats all of the tubers germinated, and the table shows that there is a greater chance of securing a stand of between 83 and 98 per cent. than lower.'

The viability of tubers is injured or ruined if they heat or sweat to any extent; hence, if they have been treated with a solution, as for scab, it is essential that they be planted at once or spread thinly to dry. Potatoes may be ruined for seed purposes, if frozen, or if shipped in bags or barrels which have contained substances injurious to the buds-as, sugar, nitrate of soda, etc.; and even moving them on the farm in unwashed sugar-bags has been found to be dangerous. Immersion in water for more than a day may destroy the buds, and probably cause the tuber to decay in a few days. By this means potatoes have been destroyed in pits and in the field when floods have occurred. Soaking them in too strong a solution of formalin or other preservative is liable to reduce viability, because the formalin tends to preserve the tuber and prevent its decomposition.

Potatoes which have been subject to diseases may be weakened and their vitality impaired.

1 From data in Ohio Exp. Sta. Bul. 145, p. 21.