68 MAIXE AGRICULTURAL EXPERIMEXT STATIOX. 



fully screened before being used and thoroughly mixed with the 

 phosphates and other plant foods. 



In each period twelve boxes were used for each kind of plant. 

 In the first box the acid rock was used ; in the second, the 

 untreated Florida rock, or "floats ;"' in the third, the phosphate 

 of iron and alumina, or Redonda; the fourth box received no 

 phosphate. The next four boxes were treated in the same man- 

 ner, and so on to the end. Thus it will be seen that for each 

 kind of plant there were three boxes which received exactly the 

 same treatment. In addition to the phosphates, each box 

 received ten grams sodium nitrate, five grams potassium chloride 

 and five grams magnesium sulphate. In the boxes where the 

 Redonda was used, ten grams calcium sulphate were also added. 

 It was intended to supply all the elements essential to the healthy 

 development of the plants except that every fourth box received 

 no phosphate. All the other conditions were made as uniform 

 as possible in order that the differences in growth might fairly 

 be attributed to the differences in the phosphates used. 



KIXDS OF PLAXT5 GROWX. 



Eighteen species of plants were chosen, representing seven 

 orders: peas, horse-beans, clover and alfalfa (Leguminosae) ; 

 turnips, ruta-bagas, cauliflower and kohl-rabi (Cruciferse) ; bar- 

 ley, corn, oats and timothy (Graminese) ; tomatoes and pota- 

 toes (Solanacese; ; carrots and parsnips f Umbellif erse j ; buck- 

 wheat (Polygonacesj ; sunflowers (Compositce). 



It was intended to carry each plant through three periods of 

 growth, but the clover, the common red species (T. pratense), 

 could not be matured in the time required for the other plants 

 and but two crops were grown. The sunflower and buckwheat 

 did not thrive under the conditions of the experiment and after 

 a single trial were replaced by carrots and parsnips, which were 

 grown for the two following periods. The seed was carefully 

 selected, that only being used which was well formed and of 

 uniform size. Of the larger plants, four or five were grown to 

 each box. The smaller plants were thinned so that the number 

 to each box was uniform for that plant. Such leaves as ripened 

 before the plants matured were removed, dried and added to 

 the plants when harv'ested. Xo attempt was made at pollination. 



