608 SUMMARY OF CURRENT RESEARCHES RELATING TO 



investigator found that roots damaged near the tip and prevented from 

 curving by placing in plaster, show when removed from the plaster 

 traumatic curvature precisely similar to that which would have taken 

 place at first. He regarded this as indicating a latent period, which 

 might be as long as eight days. The present writer, however, finds that 

 the ultimate effect is due merely to continuation of the stimulus, which 

 persists until the regeneration of the damaged portion is complete. 



Effect of Leaf-fungi on the Productive Power of the Plant.* — As 

 many cultivated plants suffer from spotting and partial destruction of 

 their leaves from the attacks of various parasitic fungi, Aderhold has 

 attempted to estimate by artificial methods the exact amount of damage 

 done. He removed leaves from cereals and from beet plants, and 

 found that in the case of barley the ears were 57-59 p.c. smaller in 

 bulk when the leaves were all removed. Somewhat similar results were 

 obtained in the case of the beet. The effect of fungicides on the leaves 

 was also calculated ; either no effect was produced, or the yield was 

 perceptibly larger. 



Resistance of Dried Plants to Poisonous Substances.! — Walther 

 Kurzwelly experimented on various seeds and fruits, and on fungus 

 spores, yeast cells, and bacteria. The fungi selected for experiment were 

 Aspergillus niger, Phycomyces nitens and Saccharomyces cerevisice, and the 

 poisons employed were alcohol, ether, benzol, carbon bisulphide, and 

 chloroform. These were used in solution or as gases. The fungi were 

 grown on sterile media and dried in sterilised paper two weeks or more. 

 The principal results are summed up as follows : — Vegetative forms of 

 the plant are less resistant to poisons than resting forms. For both 

 forms it was found that fresh examples succumbed sooner than dried 

 specimens, and that those dried in paper were more resistant than those 

 dried in air, but in all cases the poison penetrated the tissues sooner or 

 later. Spores digested in water were destroyed more quickly than dried 

 spores ; in this case much depended on the solubility in water of the 

 poisons. The author found further that the addition of water to the 

 poisons increased their action ; and that as gases they acted still more 

 quickly. By drying, the capacity to resist high temperatures was greatly 

 increased. Details are given of the various experiments, and the time 

 required to get results. 



Chemical Changes. 



Effects of Toxic Agents upon the Action of Bromelin.J — J. S. 

 Caldwell has made a series of experiments with a view to ascertaining 

 whether a similarity existed between the effects of poisonous metals 

 upon the action of an enzyme and those observed in experiments upon 

 living organisms. Bromelin, the proteolytic enzyme in the juice of the 

 pine-apple, was chosen as a typical vegetable trypsin. It was necessary 



* Praktische Blatter Pflanzenb. nnd Pflanzensch., hi. (1905) Heft 2, pp. 14-17- 

 See also Centralbl. Bakt., xiv. (1905) pp. 746-7. 



t Jalirb. wiss. Bot., xxxviii. p. 291. See also Centralbl. Bakt., xiv. (1905) pp. 

 751-4. \ Bot. Gazette, xxxix. pp. 409-19. 



