The term "monosaccharides," as commonly used, refers to hexoses. It applies equally well, however, to any other sugar-like substance which either occurs naturally or results from the decomposition of more complex carbohydrates, and which cannot be further broken down without destroying its characteristic aldehyde-alcohol groups and sugar-like properties. All such monosaccharides, being alcohol-aldehydes, can easily be reduced to the corresponding polyatomic alcohols, containing the same number of carbon atoms as the original monosaccharides, each with one OH group attached to it. All aldose monosaccharides are converted, by gentle oxidation, into the corresponding monobasic acid, having a COOH group in the place of the original CHO group. Further oxidation either changes the alcoholic groups into COOH groups, producing polybasic acids, or breaks up the chain. When ketose monosaccharides are submitted to similar oxidation processes, they are broken down into shorter chain compounds. The various monosaccharides which have thus far been found as constituents of plant tissues, or as parts of other more complex compounds which occur in plants, are shown in the following table: _Trioses_ (C_{3}H_{6}O_{3}) _Tetroses_ (C_{4}H_{8}O_{4}) Aldose--Glyceric aldehyde, Aldoses--_d_- and _l_-Erythrose, or glycerose _l_-Threose Ketose--Dioxyacetone _Pentoses_ (C_{5}H_{10}O_{5}) _Methyl Pentoses_ (C_{6}H_{12}O_{5}) Aldoses--_d_- and _l_-Arabinose Aldoses--Rhamnose _d_- and _l_-Xylose Fucose _l_-Ribose Rhodeose _l_-Lyxose Chinovose _Hexoses_ (C_{6}H_{12}O_{6}) Mannitol series Dulcitol series Aldoses--_d_- and _l_-Glucose _d_- and _l_-Galactose _d_- and _l_-Mannose _d_- and _l_-Talose _d_- and _l_-Gulose _d_- and _l_-Idose _d_-Altrose _d_-Allose Ketoses-- _d_-Fructose _d_-Tagatose _d_-Sorbose _Heptoses_ _Octoses_ _Nonoses_ (C_{7}H_{14}O_{7}) (C_{8}H_{16}O_{8}) (C_{9}H_{18}O_{9}) Glucoheptose Gluco-octose Glucononose Mannoheptose Manno-octose Mannononose Galactoheptose Galacto-octose Persuelose Sedoheptose