452 University of California Piiblications in Botanxj [Vol. 5 



A thorough review of and commentary upon the literature dealing 

 with the light requirements for germination in general appeals to 

 the writer as important in view of the divergent results obtained by 

 different investigators. Such a review is in progress and in the present 

 report no attempt will be made to correlate the results listed with 

 those of other workers. 



I am indebted to Miss E. E. Keith for valuable assistance in set- 

 ting up the experiments and recording the germinations. 



The following list of varieties of N. Tahacum and N. rustica with 

 their numbers in the University of California Botanical Garden 

 (U. C. B. G.)- will serve to identify the individuals included in the 

 table and discussion below. 



12/07 — Nicotiana rustica var. asiatica. 



13/07 — N. rustica var. brasilia. 



14/07 — N. rustica var. humilis. 



15/07 — N. rustica var. jamnicensis. 



16/07 — N. rustica var. scabra. 



22/07 — N. Tabacum var. viacropht/Ua. 



25/06 — N. Tabacum var. macrophylla purpurea. 



71/05— N. Tabacum "Brazilian." 



72/05— iV. Tabacum "Cavala." 



78/05— iV. Tabacum "Maryland." 



The seed was prepared for germination as described in previous 

 papers.^ For certain of the experiments (cf. table, note 2) a glass- 

 sided germinating case was provided. In this germinating case a 

 40-watt tungsten electric light bulb was hung and the ventilation so 

 regulated that the temperature was approximately' constant at 30 °C. 

 The seeds to be subjected to continuous darkness were placed in paper 

 collar-boxes and the boxes put into the germinating case. The dupli- 

 cates were placed in the germinating case exposed to the light of the 

 electric bulb day and night. In the remaining experiments no attempt 

 was made to regulate the temperature, and the seeds in collar-boxes 

 and undarkened were placed near a window but at no time in direct 

 sunlight. For an^' two sets of the same seed — one in darkness and 

 one in diffuse light — the range of temperature variation was the same 

 when the germination took place out of the germinating case, as in 

 all such cases the two tests were set up on the same day. The tests 

 were examined on the davs indicated in the table below and the 



2 Cf. Setchell, W. A., Studies in Xicotiana I, Univ. Calif. Publ. Bot., vol. 5. 

 no. 1, pp. 1-86, 1912. 



3 Goodspeed. T. H., Notes on the germination of tobacco seed, Univ. Calif. 

 Publ. Bot., vol. 5, no. 5, pp. 199-222, 1913; idem, ibid., vol. 5, no. 7, pp. 233-2-18, 

 1915. 



