Storage cells 173 Storage cavities 176 Crystal cavities 176 Mucilage cavities 176 Latex cavities 176 Oil cavity 178 Glandular hairs as storage organs 178 Storage walls 179 CHAPTER IX CELL CONTENTS Chlorophyll 182 Leucoplastids 183 Starch grains 183 Occurrence 184 Outline 185 Size 185 Hilum 185 Nature of hilum 188 Inulin 194 Mucilage 194 Hesperidin 196 Volatile oil 196 Tannin 196 Aleurone grains 197 Structure of aleurone grains 197 Form of aleurone grains 197 Description of aleurone grains 198 Tests for aleurone grains 198 Crystals 200 Micro-crystals 200 Raphides 200 Rosette crystals 202 Solitary crystals 205 Cystoliths 210 Forms of cystoliths 210 Tests for cystoliths 215 PART III HISTOLOGY OF ROOTS, RHIZOMES, STEMS, BARKS, WOODS, FLOWERS, FRUITS AND SEEDS CHAPTER I ROOTS AND RHIZOMES