RECENT ADVANCES IN SCIENCE 37 



tion of " light-sensitive " seeds. It has long been known that 

 the seeds of some plants do not germinate in light, whilst others 

 do not germinate in the absence of light. For instance, Kinzel 

 (" Teleologie der Wirkungen von Frost, Dunkelkeit und Licht 

 auf die Keimung der Samen," Ber. d. deidsch hot. Gesellsch., 

 XXXV, 1 91 7, p. 581) records his experience with seeds oiAqitilegia 

 atrata which were kept on moist blotting-paper in the dark for 

 ten years (1907-1917). During the first twelve months only 

 10 per cent, of the seeds germinated ; the remaining 90 per 

 cent, lay dormant in a perfectly healthy condition for the 

 whole period of ten years until exposed to light, when about 

 60 per cent, of them germinated in fifty days. Experiments 

 conducted by E, Lehmann (" Ueber die minimale Belichtungs- 

 zeit, welche die Keimung der Samen von Lythrmn Salicaria 

 auslost." Ber. d. deidsch bot. Gesellsch., xxxvi, 191 8, p. 157) 

 showed that fully imbibed seeds of Lythrum Salicaria, only 

 a negligible quantity of which had germinated in darkness, 

 gave a germination of 50 per cent, in 24 hours after a very 

 brief (tV second) exposure to a light intensity of 730 candle- 

 power at a distance of one metre. 



It has been shown that many organic and inorganic sub- 

 stances have the power of partially or completely counter- 

 acting the retarding effect of light or of darkness upon the 

 germination of light-sensitive seeds. Kiihn (" Dunkelkeimer 

 und Substrat," Ber. d. deidsch bot. Gesellsch., xxxiv, 1916, p. 369), 

 working with seeds of a number of plants, studied the inter- 

 relations of various mineral acids and of light and darkness 

 as factors influencing germination. With seeds of Phacelia 

 tanacetifolia on filter-paper moistened with distilled water he 

 obtained 80 per cent, germinations in the dark, but only 18 

 per cent, when exposed to light. By substituting weak solu- 

 tions of various mineral acids (o-i M) he was able to raise the 

 number of germinations in light to 60-80 per cent. In the 

 dark, however, the acids appeared to have no effect upon the 

 germination of these seeds. Results of a similar nature were 

 obtained with seeds of Solanum Lycopersicum and Amaranthus 

 atropurpureus . 



Gassner (" Untersuchungen uber die Wirkung des Lichtes 

 und des Temperaturwechsels auf die Keimung von Chloris 

 ciliata," Jahrb. d. Hamburger Wiss. Anstalten, xxix, 191 1, 

 Beih. 3 : " Ueber die keimungsauslosende Wirkung der Stick- 

 stoffsalze auf lichtempfindliche Samen," Jahrb. f. Wiss. Bot., 

 Iv, 1915, p. 259 ; and " Beitrage zur Frage der Lichtkeimung," 

 Zeitschr. f. Bot., vii, 1915, p. 609), who worked with seeds of 

 Chloris ciliata, found that at temperatures above 20° C. light 

 exercised a favourable effect upon the germination of these 

 seeds, whereas at lower temperatures, i.e. below 20° C, it had 



