1897.] PUBLIC DOCUMENT — No. 38. 37 



Plat 10, muriate of potash ; and Plat 11, high-grade sul- 

 phate of potash, in both cases at the rate of 200 pounds per 

 acre. The seed was sown at the rate of 3 pounds per plat. 

 The plants were Ijadly thrown out of the ground during the 

 winter, but most of them survived. The growth, however, 

 was poor, and both were cut June 19, yielding: Plat 11, 

 200 pounds ; Plat 12, 285 pounds, green weight. 



It was noticed that isolated plants or clumps of plants 

 while growing had a much deeper shade of green, and were 

 in many instances three times the average height of the 

 other plants in the field. Examination revealed the fact that 

 in every instance the roots of these plants were thickly set 

 with the nodules characteristic of the Leguminosa?, while 

 such nodules were either entirely or almost entirely absent 

 from the roots of the feebler plants, which class included 

 a large majority of those in the plats. It is believed that 

 this difi'erence accounts for the wide variation in the difi'er- 

 ent plants. These nodules are due to the development 

 upon the roots of specific bacteria (microscopic fungi). 

 These l)acteria must develop, like other plants, from seed ; 

 and this seed, when the culture of a new crop of this class 

 is first begun in a given locality, is not present as a rule in 

 such quantity as to insure a full development of the nodules. 

 Such as do develop must come from spores which adhere to 

 the seed of the new crop. In the case of a second or later 

 crop the spores are more abundant, for, as is often the case 

 with weed seeds, the few developed the first j'ear, remain- 

 ing in the soil with the roots of the crop, retain their 

 vitality, and accordingly the crop does better when grown 

 a second or third time than at first, because the more abun- 

 dant spores cause a more abundant development of root 

 nodules upon which the assimilation of free atmospheric 

 nitrogen depends. 



In this case sweet clover had never been grown upon 

 these plats before ; hence, as there were probably no spores 

 in the soil, and nodules could come only from the few 

 spores which happened to adhere to the seed sown, there 

 were in the aggregate but few and the crop did poorly. 

 The plats have been sown again with the same crop, in the 

 expectation that in the second year of its culture it will do 



