(ic) 
than the free air. The results of analysis at the end of the experi- 
ments showed that under the transparent glass the weight of the roots 
was the same as in the free air, but the weight of the leaf was much 
more, the weight of the sugar much less, and the weight of the nitrous 
salts much greater. Under the black glass the weight of the roots 
was 4 per cent of that in the free air, and the weight of the leaves 
was about 25 per cent, the weight of sugar 2 per cent, and the weight 
of the salts 8 per cent, thus demonstrating an almost complete stop- 
page of the vital processes. 
Evidently the action of these artificial coverings on the experi- 
mental plants is perfectly analogous to the action of cloud and fog in 
nature. 
It is commonly said that on the seacoast the action of the salt brine 
blown by the wind up over the land is to stunt or prevent vegetable 
growth, but the same effect must be produced by the absence of sun- 
light in those regions where fog and cloud prevail. 
INFLUENCE OF SHADE ON DEVELOPMENT. 
According to Marchand (1875, p. 130), the influence of a dimi- 
nution of sunlight on the development of the plant is apparent in the 
relative growth of plants on sunny and cloudy days or in sunny and 
shady places, but the matter was brought to exact measurement by 
Hellriegel. His experiments on barley gave him these results: 
Weight of harvest of barley. 
Plants raised— Straw. Seed. 
Pounds.) Pounds. 
rigs openiair 222th e os s2te ee - 1h RASS ids ASAE SARL PSY Sey 2 SU TSE ae Mee | 11. 44 | 10:10 
10.99 11.19 
imaereenhouse in dinectisunshinelss-s--- 26854. <2 2-2 8 ee ee | 6.72 2.86 
6. 32 3.26 
Inia greenhouse in diffuse light only —-/-..- 2-_25_----. 022 22S sc.2 228... Utes | 3. 40 | poe og 
PATO) IS crepe ee 
We see here that plants living in the greenhouse, receiving sun- 
light that has traversed the glass, have experienced a considerable 
diminution in their development as compared with those in the free 
air which experienced the full chemical force of the sunshine. The 
plants living under glass and in the diffuse light developed only a 
small quantity of stalk and did not perfect the seed at all. 
INFLUENCE OF LONG AND SHORT WAVES OF LIGHT. 
Vochting (1887) investigated the formation of tubers as influenced 
especially by sunlight. Sachs had maintained that the germination 
was entirely prevented, or at least went on very slowly, if sunlight, 
