122 BACTERIA IN RELATION TO PLANT DISEASES. 
the inoculating materials and the methods of inoculation, the cases where results of inoculation are 
completely lacking will be exceptions.” 
: The third group of 25 experiments all showed positive results from the inoculation. One of these 
reported by Gerlach was peculiar in that while the green substance showed an increase in weight, 
the weight of the dry substance fell below that of the uninoculated plants. These plants were subject 
to a long drought during the middle period of their growth. Hiltner observed the same phenomenon 
with soy-beans which ripened late, though under favorable weather conditions the growth of the soy- 
bean is increased by the presence of nodules. 
In one set of experiments it was noticeable that the small, seeded species gave good results from 
seed inoculation while with large seeded species such as peas and lupins, the results were either 
doubtful or negative. This was probably due in the case of the large seeds to the inhibiting action 
of excretions from the seed-coat. 
Another grower obtained a gain of 50 per cent in straw and seed with soy-bean. Hiltner who 
saw and examined the mature crop early in October, states that the roots of the uninoculated plants 
were free from nodules, while nodules were formed on about 50 per cent of the plants in the inoculated 
lots. 
r In another case where poor soil was used the inoculated vetches were backward compared to 
the uninoculated; later, however, they outstripped them with a more luxuriant green and a denser 
mass but the weeds also seemed to grow better there. 
Director H. Rose obtained striking results with serradella and yellow lupin. The seeds were 
carefully inoculated and sowed in good weather. The field used was a new, light sandy, rather moist 
heather land, which had borne previously only rye, fertilized with lime-kainit-phosphate and Chile 
saltpeter. 
cee this experiment 500 kg. of Thomas-meal and 600 kg. of kainit per hektar was applied in the 
spring. The seeds were sown on May 11. The weather was very dry, only two rains occurring during 
the whole summer. Growth which began slowly in the serradella took on new life late in June in the 
inoculated plots, so that early in July while the plants of the uninoculated plots were barely 10 cm, 
high, unbranched, yellow, and sickly with absolutely no nodules, those in the inoculated plots were 
20 to 30 cm. high, branched so as to form a close mat and with roots full of thick, watery nodules. 
The results with lupin were similar but less marked. The harvest of serradella (Ornithopus sativa) 
is given below: 
Plot. Greenweizht. | . Seed. 
| 
+ | 
I. Uninoculated, per hektar...| 5,300kg. | 410kg. 
III. Uninoculated, per hektar...| 6,800 kg. | 470 kg. 
II. Inoculated, per hektar...... 12,250kg. | 680kg. 
IV. Inoculated, per hektar...... 11,750 kg. 615 kg. 
Hiltner also saw the crops of Tacke, Director of the Moor Station at Bremen, just before they 
were harvested, and states that of the uninoculated plants, most were suffering hunger. There were 
yellow lupins, blue lupins, scarlet clover, and serradella. A few plants showed by their growth the 
presence of nodules, but others (yellow lupin and scarlet clover) possessed large nodules which were 
completely inactive. On yellow lupin, seed-inoculations gave no improvement over the check but 
inoculation with infected soil gave a luxuriant crop, 80 cm. high, all plants having nodules which were 
arranged in rows mostly on the lateral roots. 
Blue lupin gave similar results. About 30 per cent of the uninoculated plants formed on the 
deeper roots a few nodules which exerted little influence on the growth. Seed-inoculation gave 35 
per cent of nodule-bearing plants which, however, did not show any benefit from the nodules, which 
were on the lateral roots and hence due to spontaneous infection. Inoculation with infected soil 
produced luxuriant growth, all the plants bearing numerous nodules. Inoculation with natural earth 
gave equally good results. 
Uninoculated crimson clover was extremely scanty and sickly in growth in spite of nodules on 
the roots of all the plants. Here seed-inoculation gave the best results, with numerous nodules on 
all parts of the roots. 
Uninoculated serradella was also sickly, Seeds which were soaked before sowing gave by far 
the best results. 
These experiments brodght out the fact that in all cases uninoculated plots, or plots inoculated 
with pure cultures, were almost entirely free from weeds, while those on which natural soil inocula- 
tions were made were overgrown with weeds, especially wild spurry which is hard to eliminate. This 
observation has been repeatedly made by Tacke. 
