ROOT-NODULES OF LEGUMINOSAE. 121 



Successful results with serradella were obtained by Luberg on dry sandy land from seed-inocu- 

 lation which was followed by unfavorable weather. This was probably due to the fact that serradella 

 seeds are protected by a very heavy seed-coat and hence do not need the protective substance fatal 

 to bacteria. 



Inoculation by strewing infected soil seems relatively a better method than seed inoculation, 

 yet it needs improvement. Only when the soil offers to the bacteria favorable conditions for growth, 

 or when its bacterial content does not act unfavorably on them, as for example on moors and marshes, 

 can inoculation with soil either before or after sowing be used with any certainty of success. 



Tacke obtained remarkable results with peas on newly cultivated moor-land. The crops resulting 

 from seed-inoculation were 282 per cent greater, from soil-inoculation 384 per cent larger than crops 

 from uninoculated land or seeds. Von Feilitzen obtained like results in Sweden on similar new land. 

 His seed-inoculations gave an increase of 55 per cent straw and 1 16 per cent seed. This author also 

 found an advantage in the use of nitragin over that of natural earth inoculation, as the latter caused 

 a heavy growth of weeds fatal to the crop. 



Wollney concludes from his experiments with peas, field beans, white lupins, scarlet clover, and 

 serradella, that nitragin can be successfully used only on newly cultivated soils or on soils which 

 have borne no legumes and are sandy without humus. On soils containing humus, virulent root- 

 nodule bacteria are already present and inoculations are useless. He bases this opinion on the fact 

 that nodules occurred on the roots of all the plants sowed, yet only the peas showed increased growth. 

 In all these cases, according to Hiltner, results would probably have been favorable if inoculations 

 had been made with organisms more virulent than those present in the soil. 



Schulze on the other hand, like Kiihn, expresses a belief in the future of nitragin. He claims 

 that the few cases which have been successful prove that nitragin can work, and that what is now 

 needed is elimination of unfavorable factors and improvement in the methods of application. 



The excessive claims made for the earlier nitragin against which, however, Nobbe and Hiltner 

 protested repeatedly but in vain, have undoubtedly had much to do with bringing inoculations into 

 disrepute. Hiltner thinks, however, that pure culture inoculations will in the future, in spite of all 

 obstacles, win a place in practical agriculture, and he has desired especially because of his connection 

 with the old nitragin to help on in all possible ways this view which he has never ceased to maintain. 



From 1900 on, only pure cultures were used by Hiltner. 



Although a former experiment by Loges gives favorable results from soaking the seeds before 

 inoculation, numerous experiments by Hiltner have shown that this method is not to be generally 

 recommended, since seeds so treated, although germinating readily, are especially liable to rot in 

 the soil.* Thiele failed to get a stand with either peas or beans which had been soaked 24 hours 

 before sowing since all the beans and most of the peas rotted in the ground. He attributed this to 

 dry weather prevailing before and after sowing. Hiltner, however, thinks the failure due to the 

 destructive action of soil organisms. 



Dr. Bohme, on the other hand, obtained strikingly favorable results with yellow clover by 

 soaking the seeds in a quantity of water containing the bacteria into which was sifted a little fine 

 earth, and sowing after two days when they had absorbed all the water and were dried out. The 

 inoculated plants attained a height of 160 mm. with deep green leaves 15 mm. broad, while the 

 uninoculated plants were only a few centimeters high with pale green leaves scarcely 4 mm. broad. 



In 1901, 59 experiments were carried on for Hiltner by 31 different men according to the following 

 directions : Soaking seed previous to sowing must be avoided ; the seeds should be thoroughly wetted 

 with the inoculating fluid, the excess of moisture removed by a sprinkling of dry sand, after which 

 the seed drill can be used for sowing. As at this time the injurious action of the substance contained 

 in the seed-coat had not been discovered, this factor could not be taken into account. Hence in none 

 of the experiments of 1901 was the method used which is now considered necessary. Yet the collec- 

 tive results of the year's work justified great hopes for the future. 



One group of 1 3 experiments was eliminated by the fact that dry weather prevented germination 

 or destroyed the young plants. In another group of 2 1 experiments the effects of inoculation were 

 either imperceptible or doubtful. For example, in one experiment with beans, Braun states that 6 

 weeks of drought caused the plants to wither before they had bloomed. At the beginning of August, 

 after a good rain, growth again set in and the crop reached maturity, but no effect of the nitragin 

 was observable either in foliage or fruit. In another case while inoculated serradella gave 13 per cent 

 increase in dry substance, inoculated red clover showed an equivalent loss. Concerning these results, 

 Hiltner says : 



"We also are of the opinion that results can not be obtained under all circumstances by inocu- 

 lation ; but for the present we cling fast to the hope that in the future, after further improvement of 



"Consult Hiltner's paper. Arb. a. d. Bio. Abt. f. Land. u. Forst. a. k. Ges., m Bd., Heft, i, Berlin, 1902. 



