THE THEORIES OF PHOTOSYNTHESIS 7 



ments deserve a careful study; and a brief description of the ex- 

 perimental conditions and the chief conckisions follows. The re- 

 actions were carried out in a porcelain dish, placed in a desiccator 

 which was covered with a sheet of mica, transparent to the ultra- 

 violet rays. In the dish was placed the metallic alloy which, on 

 the slow addition of a KOH solution, evolved hydrogen; carbon 

 dioxide was passed through the solution in the dish; the quartz 

 mercury vapor lamp was 5 cm. above the mica plate, and the 

 gases passed through an opening in the wall of the desiccator, to 

 be analyzed. Stoklasa states: Formaldehyde is not formed from 

 carbon dioxide and water in ultraviolet Hght; only from carbon 

 dioxide in the presence of potassium hydroxide and nascent hy- 

 drogen is formaldehyde formed by ultraviolet light; the nascent 

 condition of the hydrogen is absolutely necessary. The action 

 of nascent hydrogen on potassium bicarbonate produces formic 

 acid even in the dark. Very evidently these results are not in 

 accord with the statements of Usher and Priestley nor of Berthe- 

 lot and Gaudechon. By the continued illumination of the mix- 

 ture of CO2 and KOH i.e., potassium bicarbonate, and of the 

 nascent hydrogen, formed by the action of the potassium hydrox- 

 ide on the alloy, Stoklasa obtained a substance w^hich possessed 

 many of the properties of a hexose sugar, and whose phenyloso- 

 zone compound gave a combustion analysis corresponding to a 

 hexosozone. Based on these observations Stoklasa formulates his 

 theory of sugar synthesis from carbon dioxide and water in the 

 plant. The CO2, taken in through the stomata, is converted 

 into potassium carbonate and then to potassium bicarbonate. 

 The latter substance "while being formed" is immediately reduced 

 to formic acid, thus. 



2KHCO3 +Light-^K2C03 +HCOOH +0 

 Light +HCOOH-^HCOH+0. 



The formaldehyde is then condensed to hexoses by means of the 

 alkali. This is not the place to enter into a detailed discussion 

 of the chemistry of Stoklasa's methods and results. There are, 

 however, a few points of such vital importance to the problem 

 under consideration that they cannot be passed by. 



