WILLIAM S. HILLMAN 683 



thus clear that aging the medium under growth conditions but in the 

 absence of phuits did not render it "old" in the sense sought for here. 



4. Other variables. In the experiments so far conducted, sucrose 

 has little effect except to reduce flowering and to increase vegetative 

 growth. Fluorescent light intensities from 140 to over 600 footcandles 

 all permit rapid flowering in M medium with EDTA if given con- 

 tinuously. A single attempt so far to imitate the action of EDTA 

 with levels of citrate (10-3 m) effective on L. perpiisilla proved un- 

 successfid, and further studies of this kind are required. The unex- 

 pected and at present inexplicable observation that, under the stand- 

 ard conditions, flowering does not occur in Hutner's medium, also 

 requires further investigation. Although Hutner's contains a high 

 level of EDTA, it differs from M with EDTA in a number of re- 

 spects such as a higher pH, higher trace metal content, and the 

 presence of ammonium as well as nitrate nitrogen. 



The writer must here retract an earlier statement (7) , unfortunately 

 hasty and based on a few ambiguous experiments, confirming Kan- 

 deler's observation that L. gibba flowering is strongly dependent on 

 light quality. Attempts have been made during recent work to 

 obtain rapid flowering under incandescent light, with results in all 

 cases like those already described. Continuous incandescent light 

 filtered through 10 cm of water and at intensities from 80 to 600 

 footcandles still permitted rapid flowering only in medium with 

 EDTA, not in fresh M medium, at 26° C. A single experiment com- 

 paring strains Gl and G3 in both incandescent and fluorescent light 

 led to the same conclusion. Thus, results at present neither confirm 

 nor contradict Kandeler's report; the apparent contradiction may 

 easily be due to the use of media, temperatures, and light sources 

 unlike those used by Kandeler. 



Discussion 

 A considerable portion of the work reviewed and presented can 

 be summarized in a few sentences. When L. perpiisilla 6746 and 

 L. gibba G3 are grown aseptically on a modified Hoagland's medium 

 under fluorescent light at about 26 °C, photoperiod has no effect on 

 the flowering of either; the former flowers, and the latter fail to 

 flower, under all daylengths. The presence of EDTA at or above 

 a concentration of 10-^ M suppresses the flowering of L. perpusilla, 

 and brings about the flowering of L. gibba, under long days (e.g., 24 

 hours) but not under short (8 hours) . In a manner of speaking, the 

 former is converted from a daylength-indifferent to a short-day plant 



