No. «. DHPARTMHNT OF AGRICULTURB. ITS 



treated Florida rock, or "floats;'' in the third, (he phosphate ol 

 iron and alumina, or Kedonda; the fourth box received no phos- 

 phate. Tiie next four boxes were treated in the same manner and 

 so on to the end. Thus, it will be seen that for each kind of plant 

 there were three boxes which received exactlv 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 healthv development of the plants, 

 except that every fourth box receivd no phosphate. xVll the other 

 conditions were made as uniform as possible in order that the 

 differences in growth might fairly be attributed to the differences in 

 phosphates used. 



KINDS OF PLANTS GROWN. 



Eighteen species of plants were chosen, representing seven orders: 

 Peas, horse beans, clover and alfalfa (Leguminosae); turnips, ruta- 

 bagas, cauliflower and kohlrabi (Crusiferae); barley, corn, oats and 

 timothy (Graminae); tomatoes and potatoes (Solanaceae); carrots 

 and parsnips (Umbelliferae); buckwheat (Polygonaceae); sunflowers 

 (Compositae). 



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 harvested. No 

 attempt was made at the pollination. As very few insects were 

 present during the growth of the plants, the fruiting, as might 

 have been expected, was very irregular. As soon as the plants 

 seemed to have attained their maximum development, they were har- 

 vested, dried, weighed and the total amount of dry matter determined 

 for each crop grown. In the diagrams that follow the average pro- 

 duction for a single period is shown, the heavy lines representing 

 the relative weights of dry matter, and the last column the weights 

 in grams. 



