INSECTIVOROUS PLANTS. 153 
Desiring to obtain conclusive evidence for his claim, Vines undertook further researches. His 
former methods were unavailing in that he was unable to separate leucin or tyrosin in measurable 
quantities. His results, obtained by another method, he considers convincing. He says: 
‘Tiedemann and Gmelin observed in 1831 that on the addition of chlorine water to the liquid 
resulting from a pancreatic (tryptic) digestion, after acidification, the liquid acquires a color varying 
from pink to violet; when concentrated there is a violet precipitate. ‘This coloration is due to the 
presence of a substance which, together with leucin, tyrosin, and other bodies, is a product of tryptic, 
as distinguished from pepticproteolysis. Thesubstancein question isa chromogen termed proteinochro- 
mogen by Stadelmann, but better known by the name, tryptophan, given to it by Neumeister, and 
its presence affords a ready means of distinguishing tryptic from peptic digestions.” 
Vines’s experiments using this method with the liquid from somewhat prolonged digestion of 
fibrin by pitcher liquid of Nepenthes in the presence of either hydrochloric or citric acid, gave the 
tryptophan reaction. He also obtained this reaction in liquids resulting from the digestion of fibrin 
by both pineapple juice and papain. These produce leucin and tyrosin in larger quantities than does 
pitcher liquid. There was no evidence of bacterial putrefaction, the products of which also have 
been found to contain tryptophan, .e., there was no odor of indol or scatol. 
The action of nepenthin, as Vines ‘calls this enzym, was also tested on albumoses and peptones, 
with the result that the digested liquid gave the tryptophan reaction. Pineapple juice and papain 
thus tested reacted similarly. Controls of various sorts gave negative results. 
Hence Vines concludes that the three enzymes, nepenthin, bromielin, and papain, have essentially 
the same proteolytic action, which is tryptic. Nepenthin, however, acts only in acid liquids, while 
bromelin and papain are most active in neutral liquids. ‘Trypsin acts most readily in alkaline 
liquids. According to their mode of action, however, they may be grouped with trypsin. Vines 
thinks, also, that these investigations strengthen his suggestion that all known proteolytic enzymes 
of plants are tryptic. 
BAcTERIA IN Hop GLanps. 
In 1892, Mohl attributed the formation of lupulin in hops to the presence of a Micro- 
coccus, called by him M.humuli Launensis. ‘The organism issaid to be present inenormous 
numbers in the glands of the living hop plant. Apparently no cultures were made, only 
microscopic examinations. No conclusive evidence was advanced. After reading his 
paper and especially after studying the glands of the hop-strobile one is prepared to appre- 
ciate Braungart’s comment: ‘‘Sonderbarer Bemerkung.’’ ‘The glands are full of oil drops 
and of minute granules, some of which have an active Brownian movement when examined 
in water but do not stain like bacteria. The latter are probably what Mohl saw. 
BACTERIA WITH ALGAE. 
Kozzowitsch in 1892 to 1894 obtained marked increase of nitrogen in mixed cultures 
of alge and bacteria, but no increase in pure cultures of the alge. He assumed, therefore, 
that the alge and the nitrogen-fixing bacteria stood in a symbiotic relation to each other, 
the bacteria obtaining their carbon food from the alge. 
In 1900 Kriiger und Schneidewind studied pure cultures of various lower alge on a 
variety of culture media with and without combined nitrogen, and reached the conclusion 
that these algze were unable to obtain their nitrogen from the air. Their paper does not 
deal directly with the question of the relation of these alge to the nitrogen-fixing bacteria 
of the soil. 
In 1903, Reinke published a paper on the symbosis of Volvox and Azotobacter, in 
which he presented additional evidence in favor of the theory that Azotobacter furnishes 
nitrogenous compounds to fresh water alge, as well as to the salt-water forms, with which 
it is associated, and to the outer membranes of which it adheres closely (‘‘so fest eingenistet 
sind, dass ein Zellenverband von gewebednlicher Innigkeit entsteht.”’) 
At his request Keutner made a large number of cultures of fresh water alge from the 
plankton of Lankener Sea near Preetz, as well as from the ponds of the botanical garden. 
The cultures, left to themselves during the summer vacation, showed in October a great 
development of Azotobacter, and had furnished in the 200 cc. of nitrogen-free nutrient 
solution an appreciable amount of combined nitrogen, on an average, about 1 mg. 
As an example of these experiments the culture of Volvox is given in detail. 
