60 
SIR J. B. LAWES AND PROFESSOR J. H. GILBERT ON THE 
the presence ©f leguminous growth, in connection with which, if at all, the establish¬ 
ment of the reality of such an action would serve to explain facts as yet not other¬ 
wise hilly explained. 
5. The Experiments of Professor B. Frank. 
In the number of the ‘ Berichte der Deutschen Botanischen Gesellschaft ’ for 
August, 1886, Dr. Frank gave a paper, “ Ueber die Quellen der Stickstoffnahrung 
der Pflanzen.” At the meeting of the Naturforscher-Versammlung, held at Berlin, 
in September, 1886, he gave a further communication on the subject; and he has 
since published a paper on the position of the question, before, at, and after that 
meeting. 
He admits the probability of the conclusion of Boussingault and others, that 
plants do not directly assimilate free nitrogen. He states, however, that in practical 
agriculture it is assumed thad some plants do fix the free nitrogen of the air; and he 
refers to the experience and writings of Schultz-Lupitz, and others, on the point, 
especially during the last 10 years. Thus, Schultz-Lupitz found that certain 
Leguminosse, especially lupins, grew well in a poor soil, under the influence of mineral 
manures; and so far from a]3pearing to exhaust the soil, cereals, roots, and potatoes, 
grew well after them, as they would if nitrogenous manures had been applied. 
Frank refers to the amount of combined nitrogen coming down in rain, &c., as about 
3 kilograms per hectare (= 2‘7 lbs. per acre), per annum, and to the average amount 
of nitrogen removed in crops as 51 kilograms per hectare (= 45'5 lbs. per acre), 
apparently obtained from the air by the nitrogen-gathering plants, which are considered 
more efiective than manure and cattle feeding. He points out that the evidence is 
not conclusive, and he recognises that the question is, whether this is only Rduh-bau ” 
after all ? This can only be settled by dmect experiments. 
He had been working at the subject for three years, and now gives the results of 
the last completed experiments, those of 1885. The first question to be decided 
was—do the so-called nitrogen-gathering plants enrich the soil, whilst the same soil, 
with the same exposure, but without a plant, does not gain combined nitrogen ? 
He experimented with a humus-sand soil, finely sifted. In some cases he used 
cylinders of pottery glazed inside, 80 cm. (= 31‘5 inches) deep, and 17’5 cm. 
(= 6'9 inches) wide; in others glass cylinders, also of 80 cm. deep, but only 11 cm. 
(= 4’3 inches) wide. To the rim of each cylinder a cap of wire gauze was fixed, to 
exclude insects ; and the vessels were exposed to free air. The soils were watered 
with distilled water. One of the wide earthen cylinders, and two of the narrow glass 
cylinders, were left without a plant. In one wide earthen cylinder three lupin seeds 
were sown ; in one narrow glass cylinder two lupin seeds, in another one lupin seed 
only, and in another one lupin seed and 20 incarnate clover seeds were sowm. If 
weeds grew where there was no experimental plant, they were stocked up, but if in 
tlie vessels with the experimental plants, they were undisturbed. 
