Micro-chemical reaction.—Both blue and yellow with iodine solution. In examining a paper containing esparto under the microscope, the pulp will be found to contain, in addition to the fibres of the fibro-vascular bundles, a certain number of the cuticular cells (see Fig. 12), together with some of the fine hairs which are seen in the section (Fig. 10). These are very characteristic. General chemical characteristics.—Pecto-cellulose mixed with some ligno-cellulose. {57} Composition (Hugo Müller):— Spanish. African. Cellulose 48·25 45·80 Fat and wax 2·07 2·62 Aqueous extract 10·19 9·81 Pectous substances, &c. 26·39 29·30 Water 9·38 8·80 Ash 3·72 3·67 STRAW.—Order, _Gramineæ_. Microscopic features.—Generally similar to those of esparto. There are, however, differences of shape and dimensions of the serrated cuticular cells, which differentiate the various kinds of straw from each other and from esparto. [Illustration: FIG. 12.] In Fig. 12 are shown these cells, from maize-straw (_a_ and _b_); from rye-straw (_c_) and from esparto (_d_). The {58} following table gives the dimensions of the cells from different kinds of straw:— Length. Breadth. Barley 0·103–0·224 mm. 0·012–0·014 mm. Rye 0·086–0·345 „ 0·012–0·016 „ Wheat 0·152–0·449 „ 0·018–0·024 „ Oats 0·186–0·448 „ 0·012–0·017 „ Another distinctive feature of straw-fibre is the presence in it of a number of oval cells, derived from the pithy matter attached to the inside of the stem. These are clearly shown at _b_ (Fig. 13), which represents the general appearance of straw pulp. [Illustration: FIG. 13.] General chemical characteristics.—Both ligno-cellulose and pecto-cellulose. The following are the results of analyses of straws (Hugo Müller):— {59} Winter Wheat. Winter Rye. Cellulose 46·60 47·69 Fat and wax 1·49 1·93 Aqueous extract 8·07 0·05 Non-cellulose or lignin 28·49 26·75 Water 9·85 11·38 Ash 5·50 3·20 BAMBOO AND SUGAR CANE.—Order, _Gramineæ_. From the close botanical relationship of these products to the stems of the gramineæ of our own climate, their microscopic features are, as might be expected, similar to those of straw. The similarity is further shown by the chemical composition (Hugo Müller):— Air-dried Cellulose 50·13 Fat and wax ·78 Aqueous extract 10·56 Lignin and pectous substances 24·84 Water 8·56 Ash 5·13