| May 15 | 7 weeks | 1 | 20.6 | 6.6 | 53.9 | 10.2 | 5.5 | 1.20 : 1 | | | | 6 | 17.8 | 5.8 | 56.7 | 9.6 | 5.4 | 1.07 : 1 | | June 18 | 12 weeks | 1 | 34.6 | 8.0 | 38.2 | 14.7 | 5.6 | 1.42 : 1 | | | | 6 | 33.4 | 7.6 | 44.5 | 15.0 | 6.7 | 1.14 : 1 | | July 16 | 16 weeks | 1 | 52.8 | 12.1 | 55.6 | 16.3 | 9.1 | 1.33 : 1 | | | | 6 | 54.4 | 10.6 | 46.2 | 19.1 | 8.8 | 1.20 : 1 | | Aug. 16 | 20 weeks | 1 | 66.8 | 9.2 | 49.1 | 17.0 | 8.3 | 1.10 : 1 | | | | 6 | 65.0 | 9.8 | 49.8 | 19.1 | 9.4 | 1.04 : 1 | | Sept. 3 | 22 weeks | 1 | 84.3 | 10.4 | 45.7 | 17.6 | 8.0 | 1.31 : 1 | | | | 6 | 86.3 | 10.2 | 45.3 | 17.3 | 7.8 | 1.30 : 1 | |_________|__________|_____|______|______|______|______|______|__________| The variations exhibited by these numbers are significant. It is clear, on the other hand, that the assimilation of the furfuroids does not vary in any important way with variations in conditions of atmosphere and soil nutrition. They are essentially _tissue_-constituents, and only at the flowering period is there any accumulation of these compounds in the alkali-soluble form. It has been previously shown (ibid. 27, 1061) that the proportion of furfuroids in the straw-celluloses of the paper-maker differs but little from that of the original straws. For the isolation of the celluloses the straws are treated by a severe process of alkaline hydrolysis, to which, therefore, the furfuroid groups offer equal resistance with the normal hexose groups with which they are associated in the complex. The furfuroids of the cereal straws are therefore not pentosanes. They are original products of assimilation, and not subject to secondary changes after elaboration such as to alter either their constitution or their relationship to the normal hexose groups of the tissue-complex. (1) CONSTITUTION OF THE CEREAL CELLULOSES (Chem. Soc. J. 1896, 804). (2) THE CARBOHYDRATES OF BARLEY STRAW (Chem. Soc. J. 1896, 1604). (3) THE CARBOHYDRATES OF THE CEREAL STRAWS (Chem. Soc. J. 1897, 1001). (4) THE CARBOHYDRATES OF BARLEY STRAW (Chem. Soc. J. 1898, 459). C. F. CROSS, E. J. BEVAN, and CLAUD SMITH. These are a series of investigations mainly devoted to establishing the identity of the furfural-yielding group which is a characteristic constituent. This 'furfuroid' while equally resistant to alkalis as the normal cellulose group with which it is associated, is selectively hydrolysed by acids. Thus straw cellulose dissolves in sulphuric acids of concentration H_{2}SO_{4}.2H_{2}O - H_{2}SO_{4}.3H_{2}O, and on diluting the normal cellulose is precipitated as a hydrate, and the furfuroid remains in solution. But this sharp separation is difficult to control in mass. By heating with a very dilute acid (1 p.ct. H_{2}SO_{4}) the conditions are more easily controlled, the most satisfactory results being obtained with 15 mins. heating at 3 atm. pressure.