290 The Botanical Gazette. . (July,. 
citing a résumé of the experiments he has made with different 
plants. He also quotes confirmatory evidence from Liebscher 
and Petermann that may now be disregarded or at least con- 
sidered of very doubtful value. 
. How far is combined N (nitrate), if used as a manure, 
utilized by the plant and what becomes of it in the soil? 
Frank holds that this subsidiary question should also be 
considered in a discussion of the nitrogen question. Most 
agriculturists affirm that if plants are fed with increasing 
amounts of nitrates a corresponding increase in N will be 
found in the crop. Frank planted mustard in N-free soil to 
which definite amounts of Ca(NO;). were added. 
The seed contained .0003™ and the soil .061™ in the form 
of the salt, while the crop showed .051%" N and no trace was 
found in the soil. An unplanted check soil containing .001% 
at the same time contained only .0046® N, thus showing that 
there is a large loss that is of no use to the plant. 
‘Repeating a part of the experiment with unplanted soil 
pots to which a definite amount of the nitrate had been added, 
a large portion of the nitrogen was found to have disappeared. 
This disappearance he thinks is due to activity of micro-or- 
ganisms of the denittifying type as shown by Breal, aS se 
ing and others, but it shows that the increased amounts 
N furnished in a manure may not reappear in the crop. They 
serve to make the plant more thrifty in the beginning and oat 
increase its ability to utilize free nitrogen. For this ra 
it is necessary to furnish combined nitrogen to non-lega 
ous plants during the germinating period while the Mi 
on the other hand can forego fixed nitrogen from the ae 
owing partly to their highly albuminous seeds and part aire 
the symbiotic relations that they maintain with the ei 
organism by means of which the assimilatory activity 
plant is largely increased. 
The actual fixation of nitrogen by legume tubercles. 
: ‘trogen 
Concerning the ability of legumes to acquire free ee 
there is no diversity of opinion, but just how these ae gen 
this gaseous element is not so definitely known. — 
erally accepted idea that the process bears an 1m F 
: : int 
tion to the presence of root nodules is no doubt correct 
main, but whether the nitrogen is fixed by the nodule ofgat" 
21 Comptes rendus Acad. 114: 681. 1892. 
