84 PHYSIOLOGY OF STREAMING MOVEMENTS 



usual shock-stoppage, often followed by a temporary acceleration, and 

 a subsequent progressive retardation, which in the case of Nitella and 

 Chara ends in a permanent stoppage in one or two hours. The temporary 

 acceleration may be due to the presence of the alcohol, and the rapid 

 fatal effect is partly due to the fact that alcoholic solutions of Veratrin 

 are slightly alkaline 1 . 



Veratrin nitrate is soluble in water, and a neutral solution containing 

 i per cent, of Veratrin in the form of the nitrate caused an immediate 

 stoppage of streaming in Chara and Nitella, lasting for eight to fifteen 

 minutes, if the solution was not removed. If streaming was still absent 

 after five to ten minutes, the addition of water usually caused an 

 immediate recommencement. After the stoppage in Veratrin and recom- 

 mencement in water have been repeated a few times, the latent period of 

 recovery in I per cent, solution of Veratrin nitrate becomes much shorter. 



After two hours' immersal in the i per cent, solution, streaming is 

 distinctly slower in cells of Nitella, but may still be present after four 

 to eight hours if the cells have been gradually accommodated to the 

 solution. Streaming permanently ceases and death ensues after ten to 

 twelve hours in i per cent., and after sixteen to twenty-four hours in 

 0-5 per cent, neutral Veratrin nitrate solution. 



Elodea yields similar results in solutions of three times greater 

 concentration. Slow streaming may still be present after twenty-four 

 hours in i per cent, solution, but after three days in i per cent, and after 

 five to seven days in 0-5 per cent, solution all the leaf-cells are dead 2 . 



None of the above substances, therefore, appears to be specially 

 poisonous to the plants examined, and in addition sunflower, cucumber, 

 and maize seedlings can withstand repeated watering with dilute solutions, 

 and continue to grow when their roots are immersed in nutrient solutions 

 containing o-i per cent, of the substances in question, although not quite 

 so rapidly as in normal media. Moreover the plants which produce 

 these poisons must be indifferent to them. Indeed various fungi (Peni- 

 cillium glaucum, Penicillium sp. ?), saprophytic bacteria (Micrococciy Bacilli), 

 as well as flagellate Infusoria, such as Monas and Bodo, will develop 

 with fair rapidity in plant decoctions containing i per cent, and 0-5 per cent, 

 solutions of Atropin, Eserin, and Muscarin. Penicillium will even grow 

 slowly on i per cent, and 0-5 per cent, solutions, to which only inorganic 

 salts have been added, the alkaloids acting here not as poisons but 

 simply as bad nutrient materials. 



A very important point to determine is whether these poisons actually 



1 The solutions of Atropin, Eserin sulphate, and Muscarin exhibited an extremely-faint acidity 

 (Griibler's preparations). 



2 The solutions must be renewed daily, since plants of Elodea slowly remove the nitric acid 

 from Veratrin nitrate, causing Veratrin to be precipitated. 



