Section B. General Characters and Character States:
X. Secretory and Excretory Structures

(Nectaries, Digestive Glands, Hydathodes, Tanniferous and Ethereal Oil Glands)

Classification based on Structure Note: No satisfactory classification scheme based on structure is available. Some glands are single-celled, most are multicellular; some are sessile, some stipitate; some are capitate, some are variously shaped; some are highly modified structures, some are so simple that they simply secrete the substance through the cuticle.

A. Classification based on Function.
(The chemical nature of the substance secreted or excreted)

Digestive. Enzyme-secreting glands found mostly on leaves of carnivorous and insectivorous plants.

Ethereal Oil Producing. Mostly aromatic compound producing glands found on various parts of the plant, without definitely known functions.

Nectar Secreting. Sugary compound producing glands found mostly on floral parts that produce attractants for pollinators.

Salt Excreting. Glands that excrete or secrete salt solutions which usually dry during the day and deliquesce at night.

Tannin Bearing. Tannin producing glands found in various parts of the plant, presumably protective in some structures.

Water Excreting. Specialized vein openings (hydathodes) through which water is lost under certain atmospheric conditions.

B. Classification based on Position.
(Location of glands on organs or parts)

Floral Nectaries

• Petaliferous. Most frequently at the base of petals.
• Sepaliferous. Most frequently at the base of sepals.
• Septal. At the junction of the septa in the ovary.
• Staminal Disc. Entire disc frequently nectariferous.
• Staminal. Most frequently at base of filament.
• Staminodial. Frequently entire structure is nectariferous.

Extrafloral Nectaries

• Bracteal and Laminar. May be localized or found over entire structure.
• Nodal. At the nodes.

Ethereal Oil Glands.

• Cauline. May be all over (general) or along the ribs (costal), or in the grooves (canaliculate).
• Laminar. May be all over (general) or near apex (acrolaminar) or near base (basilaminar) or marginal.
• Petiolar. May be all over (general) or near apex (acropetiolar) or near base (basipetiolar).