6() CARNEGIE INSTITUTION OF WASHINGTON. 



In order to deternoine whether formaldehyde condenses to sugar 

 under conditions such as possibly exist in the green leaf, an extensive 

 series of experiments is in progress with solutions of formaldehyde and 

 very weak alkalis in the sunlight and at ordinary temperatures. Thus 

 far there is no evidence that formaldehyde could condense to sugar in 

 the plant leaf in the sense of the Butlerow reaction. 



Hydratalion Capacity of Plant Colloids, by H. A. Spoehr and H. W. Estill. 



Previous work on the diurnal variation of the acidity of succulents 

 has shown the necessity of determining the effect of varying concen- 

 trations of acids and alkahs on the hydratation of plant colloids 

 before any clear idea can be gained of the effect of light on the growth 

 of these plants. An extensive study of the effect of acids and alkalis 

 on the hydratation of the colloidal material of various plants is now in 

 progress. It has become evident that the total swelling of plants like 

 Opuntia blakeana and 0. discata in dilute solutions of acids, alkalis, 

 and salts represents the summation of independent reactions of vari- 

 ous material to these reagents. Thus, solutions of acids, alkahs, and 

 salts influence the swelling and growth of these plants by affecting: 

 (1) the hydratation of the protoplasts; (2) the material that goes to 

 make up the cell- wall and fibro- vascular system ; (3) the permeability 

 and osmotic properties of the plasma-membrane. It has been found 

 that these three factors can act independently and even in opposite 

 directions. Great differences were found in these respects in different 

 portions of the same cactus joint and between young and mature ones; 

 the colloidal material of the former showed much greater swelling than 

 the latter in all solutions, and the excess of swelling in acid media above 

 that in alkaline media or distilled water was much greater in the young 

 joints. Of interest is the observation that the colloidal material from 

 mature joints which have been freed as much as possible from the 

 fibro-vascular strands showed a diminution in volume in weak alkahne 

 solution. 



The Behavior of Protoplasm as a Colloidal Complex, by Francis E. Lloyd. 

 The presence of large water vacuoles in the vast majority of plant 

 cells converts them into osmotic systems in which the behavior of the 

 emulsion colloids as such is masked to a greater or less extent. It is, 

 for example, a difficult, if not impossible, task to evaluate the hydrata- 

 tion alterations caused by various reagents because of the total change 

 in volume of the cell resulting from a gain or a loss of water by the 

 vacuoles usually referred to osmotic interchange or to change in per- 

 meability. Among other purposes before the experimental cytologist, 

 he has to account for such change in terms of structure of the col- 

 loidal complex called protoplasm. To eliminate errors of observation 

 possible when water vacuoles, being a distinct system, chiefly composed 

 of solid-disperse-phase and liquid-disperse-medium, are present, cells 



