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Oil cells
Mucilage cell, cactus
Mucilage cell, Opuntia
Non-articulated laticifer
Spurge laticifer
Laticifers
Articulated laticifers
Stinging nettle
Ducts, low mag
Duct, mag.
Wormwood duct
Young duct
Pine duct
Pine needles
Hemlock leaf
Citrus oil gland
Cotton duct
Anther endothecium
Hydathode
Glandular trichome
Venus' flytrap
Sweet olive
Sundew

Fig. 9.3-10. Transverse section of leaf of Brassica oleracea (this species has many varieties: broccoli, Brussels sprouts, cabbage, cauliflower, kale and kohlrabi). The secretory structure in this leaf is a hydathode, a gland that secretes water (see page 157 in Plant Anatomy (Mauseth) for details of the physiology). Hydathodes are supplied by a vascular bundle that ends just at the border of the hydathode or actually within it (as here). The bulk of the glandular tissue is a very open, aerenchymatous parenchyma with the special name of epithem. Often, there is a compact boundary layer (called a sheath) that separates the epithem from the rest of the leaf cells, but the hydathode shown here lacks a sheath. Epithem cells absorb mineral nutrients out of the xylem sap and transfer them to the leaf tissues, and excess water accumulates in the intercellular spaces; as the water accumulates, pressure builds and forces water out of wide stomata called water pores (arrows). The process of secreting excess water is called guttation.