In eucalyptus leaves the entire central part of the leaf, with the exception of the secretion cells and fibro-vascular bundle, is made up of the palisade parenchyma. In some leaves no palisade parenchyma occurs. Trailing arbutus (Plate 111) is an example of such a leaf. In stramonium leaves the spongy parenchyma is strongly branched; in mountain laurel the spongy parenchyma is mostly non-branched and circular in form, as in trailing arbutus (Plate 111, Fig. 3), and as occurs in the midrib portion of most leaves. [Illustration: PLATE 112 POWDERED INSECT FLOWER LEAVES (_Chrysanthemum cinerariifolium_ [Trev.], Vis.) 1. Upper epidermis. 2. Under epidermis showing stoma and hair scar. 3. Cross-section of under epidermis with attached hair. 4. Cross-section of upper epidermis. 5. Hairs. 6. Mesophyll with chlorophyll bodies. 7. Conducting cells.] In stramonium and chestnut are found rosette crystals. In henbane, coca, and senna are found prisms. In belladonna, scapola, and tobacco leaves are found micro-crystals. In most leaves no crystals occur. In witch-hazel and tea leaves stone cells occur, but in most leaves there are no stone cells. In eucalyptus, thyme, jaborandi, buchu, rosemary, and white pine leaves are secretion cells; while in belladonna, stramonium cells occur. In senna and coca leaves are crystal-bearing fibres; most leaves do not have crystal-bearing fibres. In chimaphila and uva-ursi there are no outgrowths from the epidermal cells. In senna, witch-hazel, chestnut, and coca, numerous non-glandular hairs occur on the epidermis. In tobacco, belladonna, henbane, pennyroyal, peppermint, and spearmint both glandular and non-glandular hairs occur on the epidermis. When studying leaves there should be considered the absence or presence of outgrowths and their nature; the nature of the epidermis and, when present, the number of layers of the hypodermis; the nature of the stoma, whether raised above, even with, or below the level of the epidermis; the number of layers, and the distribution, when present, of the palisade parenchyma; the form and amount of the spongy parenchyma; the absence or presence of secretion cells; the nature and form of the fibro-vascular bundles, and the nature and amount of the organic and inorganic cell contents. CHAPTER VII FLOWERS