66 CARNEGIE INSTITUTION OF WASHINGTON. 



The rapid penetration of cell-masses by acids is a well-known 

 reaction and is accompanied or followed by the extraction of electro- 

 lytes, and it has been held by some authors that when the preliminary 

 swelling which takes place in acids changes to a shrinkage death is 

 imphed. This last distinction is one without special meaning in connec- 

 tion with the present paper. 



The hydration of colloidal plates, of dried sections of plants, and of 

 fresh sections presents parallel reaction in hundredth normal organic 

 acids. The chief features of such swellings consist in an initial rapid 

 expansion followed by shrinkage due to solution or dispersion of the 

 sections. The swelling of the pentosan, agar, which has been used so 

 widely in the imbibition measurements in connection with growth, 

 would be accompanied by the solution or dispersion of material of the 

 external part of the sections and by the diffusion of whatever salts or 

 acids might be present in the interior of the mass. 



A test was carried out to determine what such loss might be in sec- 

 tions of agar and in a simple biocolloid. The agar was cast in plates 

 which came down to 0.25 mm. in thickness from a 2.5 per cent solution. 

 Strips equivalent to 200 sections, with a surface of 2,520 sq. mm., were 

 now placed in beakers of distilled water, 10 c.c. to each section of 12 

 sq. mm., for a period of 24 hours, at the same temperature. The 

 evaporation of the water showed 0.2570 gram of material had been 

 dissolved from the plates or sections which weighed 1.6731 grams at the 

 beginning, which was equivalent to about 15 per cent. This proportion 

 is to be contrasted with the 7 per cent of the soluble material dissolved 

 from sections of Opuntia, allowing for the non-soluble cellwalls. 



Another series of extractions was made with sections of biocolloids 

 consisting of 8 parts agar and 2 parts gelatine, which were heavier, 

 having a thickness of 0.38 mm. Strips of this material weighing 

 1.0316 grams, with a surface of 2,542 sq. mm., were placed in water 

 at temperatures as above for 24 hours, and when this was evaporated 

 a residue of 0.1865 gram was found, which was equivalent to about 

 18 per cent of the original. Most of this and of the material dissolved 

 from agar sections in all probability is derived from the surface layer 

 of the material, as both gelatine and agar are so nearly non-diffusible 

 as to render their extraction from the interior of the section all but 

 impossible. 



A test was arranged to estimate the relative amount of material 

 which might be extracted from plant tissues by a treatment which 

 would parallel the immersions used in obtaining swelling measurements. 

 Sections of joints of Opuntia have been used extensively in work on 

 swelling, and in order to obtain sufficient material, 24 of the custom- 

 ary size for testing under the auxograph were placed in 250 c.c. of 

 water at temperatures of 16° to 18° C, at which swellings under instru- 

 ments were also made. At the end of 24 hours the mucilaginous solu- 



