56 SUMMARY OF CURRENT RESEARCHES RELATING TO 



respect. Seeds of the latter plant were found to require a longer light 

 exposure if the other conditions of germination (dampness and warmth) 

 had been previously present. In the case of Drosera capensis, if 

 illumination was too long delayed in presence of otherwise favourable 

 conditions, power of germination was lost. In other cases presence of 

 light exercised only an accelerating effect. Remarkable differences were 

 noted in plants of the same family or even genus. 



Relations of Plant-Growth to lonisation.* — A. B. Plowman is 

 conducting a series of experiments at the Harvard Botanic Garden on 

 the relation of plants to electricity. He finds that seeds placed near 

 the anode are always killed by a current amounting to ■ 003 ampere or 

 more if continued as long as twenty hours, while seeds placed near the 

 cathode are generally but little affected, though sometimes they are ap- 

 parently stimulated by the current. He suggests that these effects are 

 produced by the electrical charges of the ions rather than by any mere 

 chemical activity of the dissociated atoms, and concludes that negative 

 charges stimulate, and positive charges paralyse, the embryonic proto- 

 plasm of the plants. In support of the latter statement he adduces the 

 fact that when a flower-pot containing lupins of about four weeks' 

 growth is charged to relatively high potential with positive electricity,. 

 the plants stop growing, gradually lose turgidity, and finally die. On 

 the other hand, when a negative charge is used, these effects are not 

 produced, but the plants are actually stimulated. 



Chemical Changes. 



Enzyme in Ripening Plantains.f — C. R. Newton discusses the re- 

 lation between enzyme action and disappearance of tannin in ripening 

 plantains. The unripe fruit contains large quantities of tannin, while 

 in the dead-ripe fruit scarcely any trace is left. Tincture of guaiacum 

 turns blue the cut surface of the unripe fruit, and the action is most 

 intense in the neighbourhood of the cells which give the strongest 

 tannin reaction with solution of iron salts, namely, those between the 

 skin and the pulp and those near the seeds. Judged by the colour test 

 plantains contain a variable quantity of enzyme. Those grown in the 

 plains had the most, those in the hills, which require to be hung for a 

 long time, often months, to ripen, have a much less quantity, and the 

 wild ones, that never lose their very astringent taste, the least of all. 

 This suggests that the action of an enzyme on the tannin is one of the 

 principal factors in the ripening of the fruit. 



Yeast Ferment.} — Th. Bokorny, of Munich, gives us the results of 

 his research on the proteolytic enzymes of yeast. He discusses the 

 quantities produced, and then compares the results with those produced by 

 pepsin and trypsin. The author attacks several other problems : the 

 distinguishing of the different proteolytic effects produced in the yeast ; 

 the most favourable conditions of acidity ; and the influence of nutri- 

 tion on the production of enzymes. 



* Amer. Journ. Sci., ser. 4, xiv. (1902) pp. 129-32. 

 t Indian Garden and Planter, April 24, 1902. 

 % Beih. z. Bot. Centralbl., xiii. (1902) pp. 235-64. 



