AND OF PLANTS UPON THE ATMOSPHERE. 
175 
Scheme of Experiments. 
Part I.— ON THE ACTION OF LIGHT UPON PLANTS. 
I. Solar light. 
A. direct. 
'Immersed in water. 
1. In causing the leaves 
to emit oxygen, and 
to decompose car- 
bonic acid 
.In atmospheric air. 
Tried with 1. Brassica oleracea-, 2. Salicor- 
nia herb ace a ; 3 . Fucus digitatus ; 4. Tus- 
silago hybrida ; 5. Cochlearia Armor acia ; 
6. Mentha viridis; 7. Rheum rhaponti- 
cum; 8. Allium ursinum ; and several spe- 
cies of Graminece. 
Tried with Geraniums. 
2. To become green 1 
when etiolated. . . . / 
Tried with Beans. 
^ritability^ 1 Tried with the Sensitive Plant (Mimosa pudica). 
^thek^kave^s ater ^ } Tried with Vines, Dahlias, Helianthuses, Lavatera arborea, &c. 
To absorb the same 1 Tried with plants of Helianthus annuus, Sagittaria sagittifolia, 
by their roots . . . . / Vines, &c. 
B. diffused or 
reflected. 
Its influence compared with'] Tried with the Geranium, Myrtle, and Polypodium, so far 
that of direct solar light > as regards its relative influence in causing the emission of 
in the above particulars. J oxygen. 
II. Artificial light, obtained A. from lamps. Tried by Professor Decandolle. 
B. from incandescent lime. Tried by myself, but no influence deteeted. 
Proportion between 
the effects attribu- 
table to their action < 
during the night and 
during the day. 
During fine weather, and 
in bright sunshine. 
During bad weather, or in 
diffused light. 
Of plants without flowers, 
and with 
Part II.— ON THE ACTION OF PLANTS UPON THE ATMOSPHERE. 
Maximum in- 
crease per cent, 
of oxygen. 
’ Cupressus 2 
Cedrus 3 - 75 
Syring a vulgaris .. 8' 75 
Ditto 6-50 
leaves alone, <J Pelargonium 2 - 00 
Ditto 5-00 
Crassula, 2 sp 0 - 00 
Mesembryanthemum 2 - 40 
Dahlia 3 ’00 
Of plants with flowers and f Dahlia 3‘75 
leaves. \ Helianthus l'OO 
’ Syringa persica 3 per cent. 
Geranium, Myrtle, Fern, as noticed above. 
viz. 
II. Proportion between 
absorbed and oxygen 
the carbonic 
evolved. 
acid f ex P er i ments show that when plants are confined the former is 
1 < always greatest at first ; but this may not continue to be the 
|_ case after a certain interval. 
III. Greatest amount of oxygen that can be 
added to the air of a jar by the influence 
of a plant. 
My experiments show that at least 18 per cent, of oxygen may 
be so added. 
IV. At what stage in the scale of vegetable 
life the function of purifying air stops. 
'Probably where there cease to be leaves. — I have shown that it 
exists in dicotyledonous and monocotyledonous, in evergreens 
and deciduous, in terrestrial and aquatic plants, in the green 
parts of succulents as well as in ordinary leaves, in Algae and 
in Ferns as well as in phanerogamous families. 
.Prof. Marcet has shown that it does not take place in Fungi. 
