ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 207 



Physiology. 

 Nutrition and Growth. 



Mechanism of Overgrowth in Plants.* — E. F. Smith has experi- 

 mented with Bacterium tumefaciens, the crown-gall organism, with the 

 object of ascertaining if the growth of tumours in plants and animals is 

 due to chemical substances liberated in the tissues of the host by para-' 

 sites. By means of careful injections from specially prepared cultures 

 the author has succeeded in causing abnormal growths in sufficient 

 quantity to allow of chemical analysis, and has proved that with this 

 species of bacterium the following substances are produced and conveyed 

 to the host-plant : — Ammonia, amines, aldehyd, alcohol, acetone, acetic 

 acid, formic acid, carbonic acid. It has also been proved that ammonia, 

 amines, aldehyd, acetic acid and formic acid are able to induce the 

 growth of tumours. The growths produced were small, but it seems 

 reasonable to believe that if the stimulus were continuous, as would be 

 the case if a living organism were attacked by a bacterium, the growth 

 would continue. The actual mechanism of these growths is primarily 

 due to a physical cause — namely, " to an increase in the osmotic pressure 

 due to the heaping up locally of various soluble substances excreted by 

 the bacteria as a result of their metabolism." These growths may be 

 regarded as continually modified wound-reactions due to the presence of 

 a parasite. 



In conclusion, the writer draws attention to the important bearing 

 which these discoveries may have upon such problems as plant-diseases 

 and monstrosities, various problems of modification by environment, the 

 distribution of dormant germ-cells among somntic cells, and the etiology 

 of various human and other animal tumours. 



Injection Experiments on Plants.! — Y. Yendo has experimented 

 with numerous vascular and non-vascular plants in order to discover 

 whether " a certain amount of a substance injected into a certain part of 

 the plant-body is conducted through the entire plant " ; also, if " the 

 effect of injection differs according to the kinds of plants, organs, and 

 tissues." The injections were carried out by means of a medical syringe, 

 and aqueous solutions of lithium-nitrate, copper-sulphate, eosin, and 

 aniline-violet were used. The author finds that the rate of conduction 

 of an injected fluid varies according to the nature of that fluid, lithium- 

 nitrate being the most easily conducted and aniline-violet the least. 

 Injected liquids usually pass to those organs where transpiration is most 

 active ; lithium-nitrate when injected into the stem travels more fre- 

 quently to the leaves than to the inflorescences ; when injected into the 

 root or cotyledon it passes to the shoot ; when injected into water-plants 

 it passes chiefly to the aerial portions, little or none going to the sub- 

 merged parts. Injections into deciduous trees during winter travel much 

 less freely than when the tree is in full leaf. Upward conduction is 

 most frequent, downward conduction less so, and transverse conduction 



* Proc. Amer. Phil. Soc. (Philadelphia) Ivi. No. 6 (1917) pp. 437-44. 

 t Journ. Coll Sci. Tokyo, xxxviii. No. 6 (1917) pp. 1-46 (2 pis.). 



