UPWARD TRANSPORT OF ORGANIC MATTER 21 



tissue. The disappearance of starch from foUage leaves 

 at night, when the sugar is allowed to be carried away, 

 and its lack of disappearance when sugar removal is 

 checked have been observed innumerable times by students 

 and investigators. The formation of starch when supplied 

 with sugar in the dark has also been repeatedly demon- 

 strated since the early work of Boehm (1883), Schimper 

 (1885), Acton (1889), and Parkin (1899). Hansteen 

 (1894), Puriewitsch (1898), Grunfeld (1926), and others 

 have shown that removal of starch from several types of 

 storage organs is largely determined by the removal of 

 soluble products, the sugars. By so conducting the experi- 

 ment as to remove the sugar produced, Puriewitsch was 

 successful in causing the loss of starch from endosperms of 

 Zea, Triticum, Hordeum, Oryza, the cotyledons oi Phaseolus, 

 Pisum, Vicia, bulbs of Hyacinth, Lachenalia, Oxalis, and the 

 rhizomes of Ranunculus, Iris, and Curcuma. He was also 

 able to remove the fat from twigs of Tilia. 



For the starch dissolution it was necessary not only to 

 remove the sugars but also to keep the tissue well aerated. 

 When merely immersed in water, the starch did not dis- 

 appear. Parkin obtained indications that aeration is 

 necessary also for starch deposition when leaves are 

 supplied with sugar solutions. When standing in the air 

 on porous blocks of gypsum which were immersed in water, 

 the sugar was carried into the water and the starch com- 

 pletely disappeared. Grunfeld w^as successful in removing 

 starch by using a number of types of porous materials. 

 When the volume of water used was small so that the 

 external sugar solution rose to a high point, about 2.5 

 per cent, further starch digestion ceased, but when the 

 volume of water was greater the dissolution was more 

 rapid and also became complete. The addition of sugar 

 to the external solution prevented starch digestion. Purie- 

 witsch also found that in many tissues, with the exception 

 of endosperms, he could bring about the redeposition of 

 starch in tissues lacking it by immersing them in sugar 

 solutions. Grunfeld was successful even in refilling endo- 



