CHANGES IN CHEMICAL COMPOSITION OF TWIGS AND BUDS OF YELLOW POPLAR DURING THE DORMANT PERIOD

During the dormant period a series of five samples of the buds and of the preceding year's growth was taken from a number of dominant and codominant yellow poplar trees. The samples were dried in an oven at 65? C, and were then ground in a ball mill until the material would pass through a 100-mesh sieve. Duplicate samples of from 25 to 50 grams were taken from this large sample, covered with 80 per cent, (by volume) aldehyde-free ethyl alcohol, and allowed to stand overnight. The liquid was decanted off and the last portion filtered through a hardened filter paper. The residue was dried at 105? C, coarsely pulverized, and extracted in a Soxhlet extractor until the percolate was colorless. The two extracts were united and made up to 1 liter with 80 per cent, alcohol. The residue from the last extraction was dried, coarsely ground, and preserved for analysis. Reducing sugars were determined by the Shaffer-Hartman method in a 200-ml. aliquot of the extract. Total sugars were determined in the reducing sugar aliquot after hydrolysis with HC1 at 73? C. for ten minutes. Total soluble nitrogen was determined in 50-ml. aliquots of the extract, and total insoluble nitrogen on 1.0-gram samples of the residue by a modification of the Kjeldahl method. A 1.0-gram sample of the residue was refluxed with 5 per cent. HC1 for four hours, and the reducing value of the solution (as glucose) was reported as total reserve polysaccharides. Starch was determined by incubation at 38? C. of 2.0-gram samples of the residue suspended in 200 ml. of water with 0.1 gram of taka-diastase. Reducing sugars were determined on the solution. Results