232 Scientific Proceedings, Royal Dublin Society. 
trioxide than before the ears of the plants had formed, and whilst 
the sulphur trioxide disappeared altogether from the lower part 
of the stem, it increased largely in the leaves and in the plant at 
large. 
Now, there are two problems to be solved in relation to the 
substitution of selenium for sulphur in plants. First.—Can selen- 
ium in the form of selenic acid replace sulphuric acid? Second. 
—Can selenium replace sulphur as a constituent of albuminous 
bodies? If it were possible, through the agency of the organs of 
plants, to effect the replacement of an element, not merely in an 
organic but in an organized body, the achievement would be one 
of the very greatest importance. Absolutely nothing has been 
done in the way of effecting the synthesis of new bodies by means 
of those wonderful combining powers which are exerted in the 
vegetable mechanism. 
The difficulty with which compounds of selenium analogous to 
the organic bodies containing sulphur are prepared, and the in- 
stability of so many of them, are facts which deter one from feel- 
ing sanguine as to the possibility of affecting the synthesis of or- 
ganized selenium bodies by means of plants; still the attempt is 
worth making. Much more hopeful is the chance of replacing 
sulphuric acid by selenic acid. Iam of this opinion from the 
results of an experiment which I made several years ago upon 
a very small scale, and which I never published up to the present, 
every year intending to repeat it upon a larger scale. The ex- 
periment was as follows :— 
A sod was taken from a field in which a crop of the so-called 
artificial grasses (which are chiefly leguminous plants, and not 
grasses at all) was just peeping over the ground. The sod was 
two feet in depth, three feet in length, and one foot wide. It 
was placed in a box, and one half of the plants were watered twice 
a week, with a weak solution of potassium selenate (K,SeO,). 
During four weeks the total quantity of potassium selenate ap- 
plied to the plants amounted to twenty grammes, which comprised 
my whole stock of the article. 
Now, this experiment was merely a tentative one. Firstly, to 
ascertain whether or not selenic acid would act injuriously upon 
plants ; secondly, to discover whether or not the selenic acid could 
partly replace the sulphuric acid, or rather could be taken up into 
