244 Puget Sound Marine Sta. Pub. Vol. 1, No. 23 



come in contact with fresh sea water. Nereocystis selectively absorbs 

 potassium chloride and it is perhaps significant that while the plant is 

 about 92 per cent water, more than one-fourth of the remaining 8 per cent 

 is KCl (6). 



These facts, coupled with the unprecedented presence of carbon 

 monoxide, make this plant of especial interest from a chemical point of 

 view. Also as a subject for photo-chemical research marine algae offer 

 an exceptional field, since by reason of their environment they are sub- 

 ject to relatively constant conditions. 



The following is a very brief mention of some of the more general 

 theories of the photosynthetic steps by which plants build up complex 

 carbohydrates from carbon dioxide and water: 



The Formaldehyde Theory, which was first suggested by Baeyer ( 1 ) in 

 1 870, has had the strongest influence in directing investigation dealing with 

 the mechanism of photosynthesis. Baeyer's theory is, essentially, that 

 under the influence of sunlight carbon dioxide is decomposed into carbon 

 monoxide and oxygen. The latter escapes and the carbon monoxide, held 

 by the chlorophyll, is reduced to formaldehyde, which condenses to sugars. 

 The steps are indicated by the following equations : 



C02-^CO-fO 

 2H+CO^HCHO 

 HCHO — » sugars 



With reference to the last step Baeyer considers that in aqueous solution 

 formaldehyde is hydrated to form CH2(OH)2 and that this condenses with 

 the elimination of water. 



Berthelot (2) in 1864 was the first to propose the dissociation of car- 

 bon dioxide into carbon monoxide and the subsequent reduction of car- 

 bon monoxide as the initial step in photosynthesis. In 1906 Loeb (4) was 

 able to break up carbon dioxide into carbon monoxide and oxygen by means 

 of the silent electric discharge. By using something to absorb oxygen, as 

 chlorophyll solutions, he obtained both formaldehyde and formic acid, and 

 en the basis of this work formulated the theory which is summarized by 

 these equations: 



COj^CO+Oj 



CO+H.O^HCOOH 



CO-fHoO-^CO^+H, 



Ha-fCO-^HCHO 



The work of Stoklasa (9, 10) is considered by some to establish the 

 formaldehyde theory on a firm basis. Stoklasa and his co-workers found that 

 formaldehyde was formed from carbon dioxide and water under the in- 

 fluence of ultra-violet light only in the presence of potassium hydroxide 



