M. C. Lea—Influence of Coior upon Reduction of Light. 355 
“No detached description of a new species should be ventured 
upon unless the author has ample means of reviewing the group 
it belongs to; and if any doubts remain of its substantive va- 
lidity, he should refrain from giving it a name till those doubts 
are clearec 
known ae and an indication of the place the new one 
we Sieben of the new plant, with analytical details, 
should never be neglected where circumstances admit of it.” 
e would heartily second these recommendations. They are 
especially applicable in this country. Time is short and the 
work before us is heavy. One grievous impediment to its prog- 
tions and comparisons, and in some cases not the know edge 
which enables them to hit the genus or even the family conrecty 
he best of us commit mistakes enough, but, it is to oped, 
is a serious hindrance. Real aid, however, is joy nly wel- 
comed, and no one in our day who is able, or desirous even to 
attempt to do systematic botanical work, has ever received 
aught but help and encouragement from those who have to “— 
the burden and heat of the day, A. GRA 
Art. XXXVII—On the Influence of Color upon Reduction of 
Tnght ; by M. Carry Lema. 
In this Journal for March of last year, I published a —_ of 
investigations which had for their object the study of the 
changes roduced in the sbnsitiveness of oben substances to 
particular rays of light, as caused by the presence of various 
colored and uncolored bodies. These results were incompatible 
with a law shortly before suhau nani by Dr. Hermann Vogel, 
as governing ek action of colored bodies on the sensitiveness 
of silver bromide. 
Dr. Vogel’s 8 was, that to render AgBr sensitive to any 
ray, or to i increase its sensitiveness, it is only nu ecessary lace 
in contact with it a substance capable of promoting the decom- 
