554 



Journal of Agricultural Research 



Vol. XIX, No. II 



numerical tuber production (Table VI) have as a group a 3-year average 

 record of 4.04 tubers per hill, while the 20 ranking lowest (Table VII) 

 have averaged for the 3-year period 2.40 tubers per hill. The number of 

 tubers produced in the hills varies from year to year, as will be shown in 

 the yearly averages of the different lines. The 108 Green Mountain lines 

 averaged 1.96 tubers per hill in 1916, 3.97 in 1917, and 2.78 in 1918. 

 Variable soil moisture conditions during the setting period are no doubt 

 responsible for a goodly portion of this fluctuation in tuber production, 

 although delayed thinning may have contributed to the low yields of 

 1916. In a general way, numerical tuber production and production by 

 weight rise and fall together, but this is by no means a fixed rule. Lines 

 of this variety show the greatest variance in numerical tuber production, 

 but this is no doubt accounted for by the more pronounced degenerate 

 tendencies among a larger proportion of these lines. Degenerate lines 

 do not fall off so much in total number of tubers produced, but a larger 

 proportion of the tubers grade below marketable size. Once degen- 

 eration begins in this variety, the line rapidly loses in vitality and yield- 

 ing power. To illustrate this we might call attention to the record of 

 line 345. This yielded 15,680 pounds per acre in 1916, while the average 

 of all Green Mountain lines for that year was 11,335 pounds. In 1917 

 it yielded 14,402 pounds as compared with an average of 26,595 for ^^^ 

 Green Mountain lines; and in 191 8 it yielded 1,366 pounds, as compared 

 with an average of 17,494 for ^^^ these lines. Expressed in plus and minus 

 variations, this line yielded 4,345 pounds above the average in 1916, 

 12,193 below the average in 1917, and 16,127 below the average in 1918. 



Table V. — Tllree-year average numerical production of marketable tubers per hill from 

 108 Green Mountain tuber lines 



Line No. 



300. 

 301. 

 302. 

 304- 



305- 

 306. 



307- 

 308. 



309- 

 310. 



in- 

 314- 

 315- 

 316. 



317- 

 318- 

 319- 

 320. 

 321. 

 322. 

 323- 

 324- 

 325- 

 326. 



Line No. 



328. 

 329- 



331- 

 332. 



333- 

 334- 

 335- 

 336. 

 337- 

 338. 

 339- 

 340. 

 341- 

 342. 

 343- 

 344- 

 345- 

 346. 

 347- 

 348. 

 349- 

 35°- 

 351- 

 352- 

 353- 

 354- 



Yield. 



3. 12 



3-65 



4. 18 



3-29 

 4.64 



4-36 

 2-75 

 3-54 



3. 02 

 2.79 



4. 06 



2. 65 



3. 21 

 2. 90 

 3.02 



3-84 



1. 19 



1-95 

 2-95 

 2- 59 

 3-40 



2. 56 



3-09 



2.87 

 2-93 

 3-93 



Line No. 



355- 

 356. 

 357- 

 358. 

 359- 

 360. 

 361. 

 362. 

 363- 

 364- 

 365- 

 366. 



i 367- 

 368. 



369- 

 370- 

 371- 

 372- 

 373- 

 374- 

 375- 

 376. 

 377- 

 378. 

 379- 

 380. 

 381. 



Yield. 



3-69 

 2.79 

 3- 40 

 2. 90 

 3- 04 



3. 06 



3-84 



37 



20 



45 

 13 

 50 

 57 

 2.44 

 2. 16 



3- II 

 3-42 



4- 32 



2. 70 



3-14 

 4.41 



3-53 

 3-38 

 2.68 

 2. 78 

 1.86 



Line No. 



382 

 383 



384. 

 385. 

 386. 



387. 

 388. 



389 ■ 



390 • 



391 • 

 392- 

 393' 

 394. 

 395' 

 396. 

 397. 

 398. 

 399' 

 400 . 



401 . 



402 . 



403 • 

 404, 



405 ■ 



406 , 

 407. 

 408. 



