4 ] Bertha Rees : 



Seeds of Acacia melanoxylon gave similar results as far as 

 swelliner was concerned. Three hours' treatment in boiling 

 alcohol and in water at the same temperature caused a number 

 of the seeds to swell on subsequently soaking in water, 

 and the power of swelling was also restored by maceration 

 for 18 weeks in chloroform at 30 deg. C When, however, 

 a comparison was made between stained sections of treated 

 and untreated seeds, no diti'erence could be detected between 

 them, and both appeared as shown in Plate 81, c. The most 

 probable explanations seemed that either theie was some 

 other material present in the outer wall which prevented the 

 cellulose reaction or that the supporting tissue was some sub- 

 stance other than cellulose. If the former were the case the 

 most likely material to mask the cellulose colour Avould be 

 tannin. The seeds were therefore tested for this substance, with 

 potassium cyanide, ammoniacal solution of ammonium picrate, lead 

 acetate and caustic potash followed by sulphurous acid, and with 

 ferric chloride,^ and in each case the result was negative. The ma- 

 terial which would be most likely to occur in the place of cellulose is 

 pectose. According to Van Wisselingh pectose is somewhat 

 like cellulose, but more gelatinous in character. In case the 

 framework should be a mixture of pectose and cellulose, the 

 sections were macerated in cuprammonia until the walls of the 

 palisade cells, which were pure cellulose, were dissolved away : 

 they were then stained with iodine and phosphoric acid, which 

 stains pectose pale yellow, but as this colour did not differ 

 much from that showD by the untreated seeds a further test 

 was necessary. Following the directions of Van Wisselingh^ for 

 the removal of pectose the seeds were boiled repeatedly in dilute 

 acids and alkalis, and washed between each operation, but this 

 treatment softened the seeds to such an extent that section 

 cutting was impossible. The second method of heating in 

 glvcerine from 25O-300 deg. C. proved more satisfactory, and 

 after half-an-liour's treatment the outer membrane was quite 

 dissolved away (Plate III. d), so it seemed that in this case 

 the framework of the cuticle was pectose and not cellulose or 

 hemicellulose. This variation in the nature of the supporting 



1 Methods jfiveii in Czai>ek Biocheiiiie. 



2 Czapek Biochemie, i., p. r)52. 



