332 EXPERIMENT STATION RECORD. 



.Of these yields 230, 227.91, and 224.1G bu., respectively, were marketable. Of 

 the very early varieties Bliss Trinmph and Crown Jewel gave the best yields. 

 In 1D07, when the season was unfavorable, the best yielding varieties were 

 Burbank vrith 132.5 bu., Early Rose with 112.91 bu., and Crown Jewel with 

 108.33 bu. of marketable potatoes. The average for both years showed Burbank 

 in the lead with 1S1.25 bu., followed by Early Rose with 170.41 bu., Beauty of 

 Hebron with 15G.24 bu.. Crown Jewel with 151.24 bu., and Gold Coin with 

 146.04 bu. Of the very early varieties Bliss Triumph led in yield with an 

 average for the 2 years of 97.91 bu. 



The influence of the time of digging was studied in 1906, when the crop was 

 dug SO, 93, and 100 days after planting. The results showed that a delay of 

 21 days in the time of digging made an increase of 136.25 bu. per acre in the 

 case of Beauty of Hebron, 126.25 bu. in the case of Burbank, and 118.75 bu. in 

 the case of Early Rose. 



On land where cowpeas had been plowed under and barnyard manure applied 

 at the rate of 15 tons per acre an increase of 51.67 bu. was obtained. Barnyard 

 manure and sulphate of potash at the rate of 100 lbs. gave an increase of 63.34 

 bu., while sulphate of potash alone at the rate of 100 lbs. gave an inci'ease of 

 20 bu., high-grade acid phosphate at the rate of 300 lbs. an increase of 25.42 

 bu., and the sulphate of potash and acid phosphate combined an increase of 

 29.66 bu. per acre. A complete fertilizer gave an increase of 10.84 bu. in one 

 instance and of 39.59 bu. in another. The best results were secured on the plats 

 on which cowpeas were plowed under. On the other plats the crop followed 

 spring oats and it was observed that these i)lats receiving barnyard manure 

 produced a larger yield than where commercial fertilizers alone were used. 

 This is considered evidence that the humus added through manure enabled the 

 soil to retain moisture to better advantage. 



Work in the improvement of the potato crop was undertaken in 1906 and 

 1907, and the results obtained showed clearly that some strains are from two 

 to three times as prolific as others, and they indicate that both yield and 

 quality of potatoes may be materially improved by selection. On the basis of 

 the yielding power of the progeny of No. 29 a planting of 25 bu. per aci-e of 

 this variety would equal 275.75 bu. per acre. Many potatoes produced only 

 about 5 lbs. of tubers from each pound of seed planted and on this basis would 

 yield only 125 bu. per acre. In connection with these tests it was observed 

 that where the seed potato was cut into 2 pieces the number of marketable 

 potatoes varied from 3 to 7 for each set planted, where cut into 3 pieces from 

 1.33 to 5.66, and where it was cut into 4 ineces from 2.50 to 7.25 potatoes. 



The skin of different potato varieties and the influence of soil condi- 

 tions, moisture, and fertilization upon the same, W. Keeitz (Arb. E. Biol. 

 Aitst. Land u. Forstw., 6 (1908), ^^o. 1, pp. 2-21, pis. 2, figs. JO).— The results of 

 different investigations on the potato and its diseases are reviewed, and the ex- 

 amination of different varieties grown on the experimental field of the Im- 

 perial Biological Institute of Dahlem is noted. In 1905, 23 different varieties 

 were grown and measurements of the thickness of the skin and the cork cells 

 were made and the form and size of the parenchyma cells and cell layers were 

 studied. 



It was found that the thickness of the potato skin is most readily determined 

 by Tisou's method. The skin thickness of individual varieties was not constant, 

 but was apparently influenced by the location of the plant and climatic condi- 

 tions. I'nder otherwise similar conditions a dry season produced a thinner 

 skin than a season with adequate rainfall. Changing the locality of the plant 

 also caused the skin thickness to vary, but when the varieties were brought 

 back to the same kind of soil the differences in this particular soon disappeared. 



