“_Parenchyma_ consists of thin-walled cells, such as are well illustrated in the interior of a corn-stalk and are found in the centre of the pepper kernel. They are often filled with starch, as in the cereals and pepper, but at times are without it, as in the mustard seed. “_Sclerenchyma_, or stone cells, are of a ligneous character, their walls being greatly thickened. They are commoner in the adulterants than in the spices, and are well illustrated in the shell of the cocoa-nut, in clove stems, and a few are seen in pepper hulls. “_Spiral and Dotted Cells_ are found in woody tissue, and their characteristics are denoted by their names. They are more commonly found in adulterants, and their presence in large amounts is conclusive, in many instances, of impurity. They may be seen in sections of cedar-wood and in cocoa-nut shells, and to a small extent in pepper husks. “_The Fibro-vascular Bundles_, as their name implies, are aggregations which appear to the eye, in some instances, as threads running through the tissue of the plant. They are easily seen in the cross-section of the corn-stalk, and are common in ground ginger, having resisted comminution from their fibrous nature. They are made up of cells of various forms. “_The Cells of the Cortex and Epidermis_ are in many cases extremely characteristic in form, and of great value for distinguishing the origin of the substances under examination. They are too numerous in shape to be particularly described, and are well illustrated in the husk of mustard, and the pod of _Capsicum_ or cayenne. “Other forms of tissue are also met with, but not so prominently as to render it advisable to burden the memory with them at first, or to seek them before they are met. “These forms of cells and their combinations which have been described, present in addition some peculiarities, aside from their structure, which assist in distinguishing them. “Parenchyma is optically inactive, and is not stained by iodine solution, except in so far as its contents are concerned. Sclerenchyma, the stone cell, is optically active, and in the dark field of the microscope, with crossed Nicols, appears as shining silvery cells, displaying their real structure. The fibro-vascular bundles are stained yellowish brown by iodine, and are thus differentiated from the surrounding tissue. “Starch is stained a deep blue, or blue black, by iodine solution, and since the contents of the parenchyma cells often consist of much starch, the parenchyma in these cases seems to assume this colour. “To distinguish some of the peculiarities of structure which have been mentioned requires some little practice and skill, but not more than is readily acquired with a short experience. There are however some aids which should not be neglected.