120 
Sydney H. Vines. 
grown under normal condilions are to be attributed entirely to the Sup¬ 
pression of the assiinilation of the former. 
To the performance of the funclion of assimilation three principa) 
conditions are essential, viz 1) the presence of light, or more accurately, 
of the less highly refrangible rays of the spectrum; 2) the presence of 
caibonic acid in the air, and 3) the presence of Chlorophyll in the leaves. 
It is possible, therefore, to investigate the etfect produced upon leaves 
by the cessation of their functional activity, by no less than four rne- 
thods; 1) the plants may be kept in the dark, as in experimenls of 
Kracs, and their assimilation thus prevented. This end vvould be ecjually 
atlained, if 2) the plants were exposed to a pure blue light, or if 3) all 
carbonic acid were removed from the air by which the plant is sur- 
rounded, as in Godlewski’s experiments; or if 4) the formation of Chlo¬ 
rophyll were prevented. 
Ihe value of the first of these four methods has already been dis- 
cussed, and, as the resulls were found to be unsalisfactory, it was not 
used. The following resulls were oblained by the last three methods. 
I. Growth of leaves in blue light. 
In availing myself of this melhod, I tnade use of the arrangement re- 
presented in Fig. 1. — It consists of a light 
wooden stand upon which a large earthenware 
saucer is placed, having in the centre a lubulaled 
opening. The plant Stands on a stage beneath 
the saucer, and the growing end of the stem, or 
of a brauch, is passed through the opening in 
the saucer, and is fixed by means of a split cork. 
Upon the saucer a large double-walled bell jar is 
placed, the space between its walls containing a 
strong ammoniacal solution of copper oxide. This 
layer of fluid, when tested with the spectroscope, 
is found to allow only the blue, indigo and violel 
rays to pass. 
The following plants were used in these ex¬ 
periments: Ampelopsis quiuquefolia, Gronovia 
scandens, Phaseolus multiflorus, Cucurbita pepo, 
Zea Mais, Tropaeolum nanum, and in all cases 
the same results were oblained. It will suffice, 
therefore, to eite a single example. 
The extremity of a branch of Ampelopsis 
quiuquefolia was introduced into the bell jar on 
June 23, and it was removed on Juue 29. When 
the experiment commenced, the portion of the branch wilhin the bell-jar 
Fig. 1. 
