35 6 The Physiology of Plants book hi 



appropriation of nitrogen by the plant, like that of carbon 

 dioxide, is dependent on chlorophyll and sunlight, basing 

 his opinion on the fact that leaves of Pelargonium, which 

 contain large quantities of nitrate, lose it in strong light 

 in a few days. 



In 1890 Frank and Otto proved that a synthesis of 

 asparagin takes place in leaves under the action of light. 

 In 1898 Hansteen published the results of a series of 

 experiments, which he made on this question. He found 

 that in darkness protein is produced from urea in the 

 presence of cane or grape sugar ; that asparagin and 

 glutamin form protein only when glucose is present ; and 

 that glycin or glycocoll needs cane sugar for the purpose. 

 In 1900 some results were published by Maliniak which 

 in the main confirm those of Hansteen. Zaleski showed 

 that a synthesis of protein takes place in the dark in 

 resting or growing bulbs, tubers, and roots, without any 

 increase of nitrogen-content, an observation confirmed by 

 Iwanoff. 



Further researches on this point made by Laurent and 

 Marchal were published early in the present century. 



This question thus still awaits solution. 



