54 CARNEGIE INSTITUTION OF WASHINGTON. 



PHOTOSYNTHESIS. IMBIBITION. AND GROWTH. 

 Studies in Photosynthesis, by H. A. Spoehr. 



The Baeyer theory of photosynthesis which for almost half a cen- 

 tury has dominated investigation in this field is being made the subject 

 of critical experimental study. The basis of this theory is the con- 

 densation of formaldehyde in aqueous solution by means of alkahes, 

 as discovered by Buterlow in 1861. No consideration has ever been 

 given to the question whether this reaction actually takes place under 

 conditions such as exist in the chlorophyllous leaf. Accordingly a 

 series of tests was undertaken to determine whether f ormose is formed 

 from formaldehyde in weak alkaline or in neutral solution and at 

 ordinary temperatures, and whether the reaction is influenced by sun- 

 light. Pure 3 per cent solutions of formaldehyde (free from methyl 

 alcohol and formic acid) were used, with the salts in N/10 concentra- 

 tion, in glass flasks. These were exposed directly to the sunlight for 

 5 months, and the amount of sugar formed determined every month. 

 Not a trace of sugar was formed by CaCOs, 3MgC03.Mg(OH)2.3H20., 

 K2CO3, KHCO3, KOH, colloidal Fe (0H)3, ui the dark or the sunhght. 

 ZnC03 formed a trace in the light, but none in the dark. Light does 

 increase the sugar formation with the stronger alkali hydroxides. 

 Pure neutral formaldehyde solutions in glass and quartz vessels formed 

 no sugar at all in the sunlight. Even then, if formaldehyde were 

 formed as the first reduction product of carbon dioxide, which has 

 previously been shown to be highly improbable, it would seem that 

 this second step in the photosynthetic process must proceed in a 

 different manner than is supposed by this theory. The whole process 

 is, no doubt, of a nature much more highly complex, involving the 

 operation of unknown enzymes in cooperation with the chloroplasts. 



The Carbohydrate Economy of Cacti, by H. A. Spoehr. 



The phenomenon of metabolism presents such a complex and mul- 

 tiplicity of molecular disintegrations and reconstructions that a com- 

 parative study of plants of different physiological behavior is of the 

 greatest importance in order to gain a clear and comprehensive con- 

 ception of this activity. The higher plants exhibit differences not so 

 much as to the course and nature of their metabolism, but rather as 

 to the accumulation of substances formed either as by-products or as 

 intermediate steps in the complete katabolism. These differences 

 are often the result of structural or environic conditions. For the 

 purpose of studying these relations the cacti offer very interesting 

 material, both on account of their structural peculiarities and the rather 

 extreme climatic conditions under which they live. Certain of the 

 characteristics of the metabohsm of these plants have already been 

 thoroughly studied by Dr. H. M. Richards. However, our knowledge 



