SEED GERMINATION IN LOBELIA, WITH SPECIAL REF- ERENCE TO THE INFLUENCE OF LIGHT ON LOBELIA INFLATA ' By W. C. MUENSCHER 2 Assistant professor of economic botany^ New York {Cornell) Agricultural Experiment Station INTRODUCTION The Indian tobacco, Lobelia inflata L., a common native annual of eastern North America, is the source of alkaloids used in certain drugs. Most of these alkaloids are obtained from wild plants. Experimental plantings have been made, however, to determine the effect of various treatments on the alkaloidal content of Z. inflata under cultivation,^ and in recent years attempts have been made to grow it commercially. Six years ago several samples of Lobelia inflata seed were submitted to the writer with the complaint that when planted the seed had failed to grow. Germination tests on these seeds had also been unsuccessful. The question then arose, Are these seeds immature, dormant, or dead? After subjecting lots of these seeds to various treatments employed to induce germination, such as alternating temperatures, chilling, freez- ing, soaking in sulphuric acid, hydrochloric acid, or hot water, and removal of seed coats, it was found that some of the samples were dead, and that strong light was necessary to obtain any germination from the others. The exact age of the seed samples was unknown, and no information was available concerning the condition of the seeds at the time of harvest. In order to obtain information on the effect of age upon the conditions necessary for the germination of L. inflata an experiment was began in 1930 with fresh seeds of known age. MATERIALS AND PROCEDURE Seeds of Lobelia inflata were obtained from six localities: (1 ) Marion, Va. ; (2) Asheville, N. C. ; (3) StatesviUe, N. C. ; (4) Chateaugay, N. Y. ; (5) Newport, Vt.; and (6) Lenox, Mass. The first three lots were commercial seeds from the crop of 1929, supplied by J. T. Lloyd of Cincinnati, Ohio. The last three were harvested from wild plants when the fruits were ripe, about the middle of September 1930. These seeds were allowed to air-dry in the laboratory and were stored in a dark case in tightly stoppered glass bottles until they were used for making germination tests. All tests were made in duplicate with lots of 100 seeds. Preliminary gerlniïiation tests were made with soil, water, paper towels, and unburned clay flower pots as substrata. The best germination was obtained in water or by placing the seeds on the moistened surface of a clay flowerpot. Small 1-inch pots were used for the germination 1 Received for publication Jan. 11,1936; issued May 1936. 2 The writer is indebted to S. R. Patrick and Helen Hazard for assistance in making the germination tests in 1934 and 1935. 3 MASCRé, M., and GéNOT, H. EXPéRIENCES CULTURALES SUR LA LOBELIE, "LOBELIA INFLATA" L. Bull. Sei. Pharm. 39: 165-172. 1932. and GÉNOT, H. NOUVELLES EXPéRIENCES SUR LA CULTURE DE LA LOBELIE (LOBELIA INFLATA L.) Bull. Sei. Pharm. 40: 453-459. 1933. ^ Journal of Agricultural Research, Vol. 52, no. 8 Washington, D. C. Apr. 15, 1936 Key no. N. Y. (Cornell)-34 (627) 628 Journal of Agricultural Research Vol. 52, no. 8 tests. The clay pots were inverted in a glass bowl of water so that the water reached within 5 mm of the surface holding the seeds. The bowls were covered with Petri dishes so as to provide a moist, well- lighted germination chamber. One series of chambers was set in a well-lighted room near a south window; the other series was placed in a dark chamber in the same laboratory room. The germinators were examined daily and the germinated seedlings were counted and removed on the ninth to twelfth day and at approx- imately 10-day intervals thereafter for 40 to 60 days. In the earlier tests the germinators in the dark were opened only in a dark room with artificial light, but later, when it was found that the short expo- sure to daylight did not affect the germination of the soaked seeds, the seeds were examined from time to time in daylight. Germination tests were made of six samples over a period of from 4 to 6 years. Germination tests of several other species of Lobelia were made, by the methods already described, in order to compare the results with those obtained with L. inflata. The following lots of seed were har- vested in the autumn of 1930 from mature fruits from plants growing wild in various parts of New York: L, cardinalis L., L. dortmanna L., L. kalmii L., and L, siphilitica L. In addition, seed of i. tenuior R. Br. and five varieties of L. erinus L. were obtained from a commercial seed dealer. DATA AND DISCUSSION The results of germination tests with Lobelia inflata seeds from 1 to 6 years of age are recorded in table 1. TABLE 1.—The germination of Lobelia inflata seeds in light and darkness [100 seeds were used in each test] Duration of germi- Duration of germi- Ger- nation test Ger- Lot no., source Year nation test mina- Lot no., source Year mina- of sample, and of tion of sample, and of tion year of harvest test in year of harvest test in Begun Ended light 1 Begun Ended light 1 Per- Per- cent cent /1930 Apr. 17 July 15 16 Í1930 May 12 July 15 80 1930 May 1 ._.do...- 59 3. Statesville, 1931 Apr. 12 Apr. 27 81 1930 May 12 __.do.-.-_ 65 N. C, 1929— -^1933 Mar. 16 Apr. 20 44 1, Marion, Va., 1931 Apr. 12 Apr. 27 67 Continued. 1934 Mar. 1 Mar. 31 36 1929. 1933 Mar. 16 Apr. 20 40 ll935 Feb. 10 Apr. 8 40 1934 Mar. 1 Mar. 31 48 Í1931 Jan. 2 Feb. 18 0 1935 Feb. 10 Apr. 8 28 4, Chateaugay, Jl933 Mar. 16 Apr. 20 28 /1930 Apr. 17 July 15 48 N. Y., 1930. 11934 Mar. 1 Mar. 31 4 1930 May 1 _..do..___ 46 1935 Feb. 10 Apr 8 20 1930 May 12 ...do...- 29 1931 • Jan. 2 Feb. 18 0 2, Asheville, N. 1931 Apr. 12 Apr. 27 55 5, Newport, Vt., Il933 Mar. 16 Apr. 20 33 C, 1929. 1933 Mar. 16 Apr. 20 4S ^, 1930. 11934 Apr. 4 May 4 93 1934 Mar. 1 Mar. 31 41 1935 Mar. 29 Apr. 28 94 1935 Feb. 10 Apr. 8 34 6, Lenox, Mass., Í1931 Jan. 2 Feb. 18 0 3, Statesville, ri930 Apr. 17 July 15 64 1930. -^1933 Mar. 16 Apr. 20 3 N. C, 1929. U930 May 1 ...do-..._ 88 1934 Apr. 4 May 4 24 1 There was no germination in darkness but when the seeds were exposed to light at the end of the 1935 germination test in darkness the following percentages of germination were obtained for the lot numbers indicated: 1, 36; 2, 23; 3, 68; 5, 97. All of the samples gave some germination in sunlight. No seeds germinated before the eighth day. Germination usually began on the ninth day, and approximately 80 percent of the total germina- tion occurred between the ninth and the twentieth days. There was Apr. 15,1936 Seed Germination and Influence of Light on Lobelia 629 considerable variation in the percentage of germination in the samples of seed from different sources. All six samples continued to remain viable for from 4 to 6 years, or the duration of the experiment. The figures for samples 4, 5, and 6 indicate a period of low germination during the first year, possibly a period of dormancy due to other factors than light. In general, the percentage of germination increased during the second to fourth year and then decreased some- what. At no time did even a single seed germinate in the germinators kept in darkness. Some of the lots of seed after having been kept in the dark for 30 to 55 days without germinating were transferred to a room where they were exposed to sunlight, and within 9 to 30 days from 23 to 94 percent germination was obtained (table 1). These germination percentages were very similar to those obtained by plac- ing similar samples of seed directly in the light. These results demonstrate the necessity of light for the germination of seeds of Lobelia inflata. It was thought that if large lots of seeds were placed in germina- tors, possibly a few seeds would be found to germinate in darkness. Accordingly, lots of several thousand seeds were scattered on the surface of water cultures and placed in dark chambers, and similar control cultures were placed in sunlight. The cultures in the light germinated well, but not a single seed germinated among those kept in the dark. To determine the influence of light on the germination of Lobelia inflata under field conditions, seeds of lots 1, 2, 3, and 5 were sown in rows in a garden (Dunkirk silty clay loam) on May 24, 1934. In one series the seeds were dropped on the surface of the soil and in another they were covered with about 1 cm of finely pulverized soil mixed with sand. No seedlings were visible before June 10, but from then on numerous plants began to appear from the surface-sown seed. Only three plants were found in the rows in which the seed had been covered. It would appear that in growing L. inflata from seed good results may be expected by sowing the seed on the surface of a finely prepared seedbed, as is frequently done with tobacco seed.* Stock- berger,^ in discussing the planting of L.