_1st. The Saccharine and Amylaceous Constituents._--These substances are compounds of carbon, hydrogen, and oxygen, and all possess a certain degree of similarity in composition, the quantities of hydrogen and oxygen they contain being always in the proportion required to form water, so that they may be considered as compounds of carbon and water; not that it can be asserted that they actually do contain water, as such, for of that there is no evidence, but only that its elements are present in the proportion to form it. _Cellulose._--This substance forms the fundamental part of all plants. It is the principal constituent of woody fibre, and is found in a state of purity in the fibre of cotton and flax, and in the pith of plants; but in wood it is generally contaminated with another substance, which has received the name incrusting matter, because it is deposited in and around the cells of which the plant is in part composed. Cellulose is insoluble in all menstrua, but, when boiled for a long time with sulphuric acid, is converted into a substance called dextrine. Cellulose consists of-- From pith of Elder-tree. Spongioles of roots. Carbon 43.37 43.00 Hydrogen 6.04 6.18 Oxygen 50.59 50.82 ------- ------- 100.00 100.00 It is represented chemically by the formula, C_{24}H_{21}O_{21}, which shows it to be a compound of 24 atoms of carbon with 21 of hydrogen and 21 of oxygen. _Incrusting matter._--Large quantities of this substance enter into the composition of all plants. Of its chemical nature little is known, as it cannot be obtained separate from cellulose, but it is analogous to that substance in its composition, and probably contains hydrogen and oxygen in the proportion to form water.