PLATE 112 POWDERED INSECT FLOWER LEAVES 268 PLATE 113 SMOOTH-WALLED POLLEN GRAINS 271 PLATE 114 SPINY WALLED POLLEN GRAINS 272 PLATE 115 PAPILLÆ 275 PLATE 116 PAPILLÆ OF STIGMAS 276 PLATE 117 PAPILLÆ OF STIGMAS 277 PLATE 118 POWDERED CLOSED INSECT FLOWER 279 PLATE 119 POWDERED OPEN INSECT FLOWER 281 PLATE 120 POWDERED WHITE DAISIES (_Chrysanthemum leucanthemum_, L.) 283 PLATE 121 CROSS-SECTION OF CELERY FRUIT (_Apium graveolens_, L.) 286 PLATE 121 CROSS-SECTION OF CELERY FRUIT (_Apium graveolens_, L.) 286 PLATE 123 CROSS-SECTION SWEET ALMOND SEED 290 PLATE 124 CROSS-SECTION OF A RADIAL VASCULAR BUNDLE OF SKUNK CABBAGE ROOT 293 PLATE 125 CROSS-SECTION OF A PHLOEM-CENTRIC BUNDLE OF CALAMUS RHIZOME (_Acorus calamus_, L.) 294 PLATE 126 CROSS-SECTION OF A CLOSED COLLATERAL BUNDLE OF MANDRAKE STEM (_Podophyllum peltatum_, L.) 286 PLATE 127 BI-COLLATERAL BUNDLE OF PUMPKIN STEM (_Curcurbita pepo_, L.) 297 Part I SIMPLE AND COMPOUND MICROSCOPES AND MICROSCOPIC TECHNIC CHAPTER I THE SIMPLE MICROSCOPES The construction and use of the =simple microscope= (magnifiers) undoubtedly date back to very early times. There is sufficient evidence to prove that spheres of glass were used as burning spheres and as magnifiers by people antedating the Greeks and Romans. The simple microscopes of to-day have a very wide range of application and a corresponding variation in structure and in appearance. Simple microscopes are used daily in classifying and studying crude drugs, testing linen and other cloth, repairing watches, in reading, and identifying insects. The more complex simple microscopes are used in the dissection and classification of flowers. The =watchmaker’s loupe=, the =linen tester=, the =reading glass=, the =engraver’s lens=, and the simplest folding magnifiers consist of a double convex lens. Such a lens produces an erect, enlarged image of the object viewed when the lens is placed so that the object is within its focal distance. The focal distance of a lens varies according to the curvature of the lens. The greater the curvature, the shorter the focal distance and the greater the magnification. The more complicated simple microscope consists of two or more lenses. The double and triple magnifiers consist of two and three lenses respectively.