In these experiments, acetylene was added to sunlight, being turned on after twilight. For com parison, the experiments were conducted in warm medium and cool (I7-50°) rooms. Lettuce, parsley and spinach were hastened ; coleus increased in vigor ; asparagus showed little effect ; begonias gave increased growth, but delayed flowering period ; Cobma seandens produced 15 to 20 per cent more vine ; ferns, leeks, onions and beets showed very little effect ; radishes in the cool house in the dark days of autumn produced more than twice the root product, the time period was increased 62 per cent, and the maturing period shortened about 20 per cent ; strawberries grew more vigorously and ripened fruit sixteen days earlier ; peas and bush beans were benefited ; pole beans produced a much heavier vegetative growth, but matured fruit later ; cucumbers were appar ently injured.
The results of the experiments may be briefly summarized. Comparing the results of the differ ent vegetables, we find (1) That with the exception of the cucumbers, all the forms had a decided increase of the foliage parts.
(2) That the time of fruit-maturing is variously affected, the strawberries and peas maturing ear lier, the tomatoes and pole beans later, and the cucumbers and other forms practically unchanged.
(3) That there is, as a rule, an increase in the amount of fruit, also in size of individual fruits, the cucumber being the chief exception.
(4) That the chief beneficial effects of the light are to make up for deficiency of sunlight, to give, with few exceptions, stronger and more vigorous top growth, and to help overcome unfavorable con ditions in certain other lines.
(5) That there seems to be a limit in rapidity of growth, beyond which plants cannot be forced at all proportional to the attendant expense. Just what conditions govern this limit or where the limit is in forcing-house plants, is as yet unknown.
Photosynthetic processes are completed to the point of starch-making ; root systems increased in the main proportionately with top development.
Influence on three exceptions, all plants bloomed earlier under acetylene light than under sunlight. Some of the geranium plants bloomed twenty days earlier. The blooming of car nations was hastened, but the stems were elongated to an injurious extent. The growth of Easter lilies was increased and the flower ing period has tened (Fig. 45).
The influence on the quantity of the bloom was marked. In every case there was an increase, two or three times as many blossoms being produced in some plants. The
effect on the duration of the bloom was some what contradic tory. Cucumber flowers remained on the vines a shorter time.
Lily and narcis sus flowers lasted longer under the acetylene. Bulb plants came to maturity under acetylene light alone with no sunlight, and other plants made green foli age (Fig. 46).
General sum mary.— These preliminarytests gave marked results, but much more experimental work must be done. Ninety to ninety-five per cent of the plants experimented with responded favor ably to the stimulus given by the acetylene light. There was no uniformity of results within a group of related plants. No striking detrimental results were observed except when plants were grown under optimum conditions.
Incandescent gaslight.
L. C. Corbett experimented with the Welsbach incandescent gaslight, the results of his work ap pearing as Bulletin No. 62, of the West Virginia Agricultural Experiment Station. These tests were of an economic rather than a scientific nature. In no case was the artificial light found to be a satis factory substitute for daylight. But it is thought that, could the conditions of the plants in the dark chamber during the day be kept as nearly normal as are the conditions for plants exposed to the arti ficial light at night only, the results would be very different. A possible explanation of the stimulus following the use of the incandescent gaslight and the incandescent electric light as well, as gathered from these experiments, is from their richness in red and orange rays. A summary of the results of Corbett's work showed : (t) The incandescent gaslight of the Welsbach burner was an active stimulus to plant growth (2) Lettuce plants subjected to the influence of the incandescent gaslight at night were taller and heavier than plants of the same variety and seed sowing grown in normal conditions.
(3) Lettuce and spinach subjected to the stimu lating influence of the light grew faster and com pleted their growth in less time than plants of the same sorts from the same seed-sowing grown in normal conditions.
(4) No injurious effects resulted from the use of the incandescent gaslight.
(5) The stimulating influence of the light as indi cated by the growth of plants used in various tests is shown by the order in which the sorts are named, the first being the most susceptible—spinach, cab bage, radish, lettuce, tomato.