236 Address of Prof. DeCandolle 
chemistry ; contrary to that which occurs in mineral chemistry, 
at least in the case of chlorid of silver. The least refrangible 
according to its intensity. It is these, also, which change the 
coloring matter of flowers when it has been dissolved in water 
or alcohol.“ Those rays called chemical, such as violet, and the 
invisible rays beyond violet, according to recent experiments, 
confirmatory of those of ancient authors—those of Sebastian 
Poggioli, in 1817, and of C. M. Guillemin—have but one single 
well-ascertained effect, that of favoring the bending of the stem 
toward the quarter from which they come more decidedly than 
do other rays; yet that is an effect perhaps more negative than 
positive, if the flexure proceeds, as many still believe, from what 
is going on on the side least exposed to the light.”* 
effect upon vegetation of the non-visible calorific rays at 
the other extremity of the spectrum have been but little studied. 
According to the experiments we have on this subject, they 
would appear to have but little power over any of the functions ; 
but it would be worth while to investigate further the calorific 
regions of the spectrum by employing Dr. Tyndall’s process, 
that is, by means of iodine dissolved in bisulphid of carbon, 
which permits no trace of visible light to pass. 
How interesting it would be to make all these laboratory ex- 
prolonged as long as desirable, and, probably, unlooked-for re- 
sults would occur as to the form or color of the organs, particu- 
larly of the leaves. : 
Permit me to recall on this subject an experiment made in 
1853 by Professor von Martius.” It will interest horticulturists 
now that plants with colored foliage become more and more 
fashionable. Prof. von Martius placed some plants of Amaranthus 
tricolor for two months under glasses of various colors. Under 
Sir John Herschell, Edinb. Phil. Journ., January, 1843. ; 
8. sh em a Scientifici, quoted by Dutrochet, Compt. Rend. Acad. Sci, 
** The rather confused and questionable explanations, founded on the notions of 
Dutrochet, of the existence of a deoxydizing power on the brightest side, clash with 
the fact that the blue, indigo, and violet rays, the least powerful for deoxydizing 
tissues, are the most powerful in causing them to 
“ Gelehrte Anzeige,” Miinchen, Dec. 5, 1853. _« 
