634 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
caffeine, Herr E. Heckel concludes that the alkaloids in the seeds are 
true reserve food-materials, since they are entirely transformed into 
assimilable substances during the process of germination. The experi- 
ments on caffeine were made chiefly with Sterculia acuminata , those on the 
three other alkaloids with Strychnos nux-vomica and Datura Stramonium. 
In all cases the alkaloids contained in the cotyledons or in the embryo 
had completely disappeared as soon as the seedlings had attained a 
considerable size, the products of the transformation of caffeine being 
glycophyll and potassium nitrate. A similar result was obtained with 
the eserine contained in the seeds of Physostigma venenosum. 
Fixation of Free Nitrogen.* — Sir J. B. Lawes and Prof. J. H. Gilbert 
have repeated Hellriegel and Wilfarth’s experiments j - on the source 
from which leguminous plants obtain their nitrogen, and their conclu- 
sions are, in the main, in harmony with those of these observers. While 
with Cruciferous, Ohenopodiaceous, Graminaceous, and all other culti- 
vated crops except those belonging to the Leguminosse, all their nitrogen 
would appear to be derived from the nitrates in the soil, this is appa- 
rently not the case with Leguminous plants, those on which the observa- 
tions were made being chiefly peas, lupins, clover, vetches, and lucerne. 
The authors consider that there is no evidence whatever that these plants 
have any power to fix the free nitrogen of the atmosphere ; but that the 
tubercles on the roots are the organs through which a large proportion 
of the nitrogen is absorbed, the bacteria which infest these tubercles 
utilizing and fixing the free nitrogen from the soil, and thus forming 
nitrogenous compounds which are taken up by the host. The most 
striking results were obtained with the yellow lupin. 
Formation of Nitrates.:]: — Herr Serno finds nitric acid present in 
almost all plants, the largest quantities occurring in the Malvaceae, 
Crucifer®, Papaveraceae, Convolvulaceae, Labiatae, Compositae, and Urti- 
caceae. In other plants it occurs only in the roots, and especially in 
the newly formed absorbing roots. In older roots it is often absent, 
and always in those which carry on a symbiotic existence with fungi. 
The author found nitric acid present in the greatest abundance in aquatic 
plants, usually, but not always, in those that grow in sandy situations, 
always wanting in marsh-plants. In many perennial plants the nitrates 
are stored up in winter as a reserve-material ; in others they are formed 
only in the spring. In annual plants they occur abundantly in all parts. 
The function of the nitric acid is believed by the author to be connected 
with the formation of amides, especially of asparagin. 
M. Berthelot§ refers to the observations of Heckel as to the 
simultaneous disappearance of caffeine and formation of potassium 
nitrate in the seeds of kola, as confirming his view that the formation 
of nitrates in plants is a similar process, from a physiological point of 
view, to the formation of nitrates in the soil, and is equally due to the 
action of microbes. 
* Proc. Roy. Soc., xlvii. (1890) pp. 85-118. Cf. this Journal, 1888, p. 261. 
f Cf. this Journal, 1889, p. 781. 
X Lanclwirthsch. Jahrb.. xviii. (1889) pp. 877-905. See But. Centralbl., xlii. 
(1890) p. 156. § Comptes Reudus, cx. (1890) p. 109. 
