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Flos Tiliae
Plant material of interest: dried inflorescences
General appearance
The inflorescence is yellowish-green. The main axis of the inflorescence
bears a linguiform bract, membranous, yellowish-green, practically glabrous,
the central vein of which is joined to about half its length with the
peduncle. Flowers are arranged in clusters of 3–7 on a stalked pendulous
cyme (T. platyphyllos) or in clusters of 3–15 on a stalked erect cyme (T. cordata).
The diameter of the flowers is between 1 and 1.5 cm. Sepals are easily
detached, oblong-ovate, greyish-green, up to 6 mm long; their abaxial surface
is usually glabrous, their adaxial surface and their borders are strongly
pubescent. The 5 spatulate or ovate, thin petals are yellowish-white, up to 8
mm long. They show fine venation and their borders are only sometimes
covered with isolated trichomes. The numerous stamens are free and usually
constitute 5 groups. The superior ovary has a pistil with a 5-lobate
stigma. The fruits are nutlets, 2 mm in diameter. The cut drug consists of
fragments of inflorescences with a diameter 0.5–20 mm (1–3).
Organoleptic properties
Odour: faint aromatic, characteristic; taste: faint, aromatic, sweetish and
mucilaginous (1–3).
Microscopic characteristics
The adaxial epidermis of the bract has cells with straight or slightly sinuous
anticlinal walls. The abaxial epidermis has cells with wavy-sinuous
anticlinal walls and anomocytic stomata. Two types of trichomes occur
near the junction of the bract vein with the peduncle: one glandular, with
short 1–3-cellular stalk, and oval multicellular head, and the other covering,
stellate, with 3–7 long sinuous cells. The mesophyll is spongious,
with clusters or prismatic crystals of calcium oxalate. The parenchyma of
the sepals, particularly near the veins, has numerous mucilaginous cells
and cells containing small calcium oxalate clusters. The adaxial epidermis
of sepals has bent, thick-walled covering trichomes, unicellular or stellate
with up to 5 cells. The epidermal cells of the petals have straight anticlinal
walls with a striated cuticle without stomata. The parenchyma of the petals
contains small calcium oxalate clusters (8–16 µm in diameter) and mucilaginous
cells. The mucilage stains pink with ruthenium red solution.
The pollen grains have a diameter of about 30–40 µm and are oval or
slightly angular with 3 germinal pores and a finely granulated exine. The
ovary is glabrous or densely covered with trichomes, often very twisted,
unicellular with 2–4 branches. The diagnostic features include the sclereids
of the bracts and the tufted trichomes of the sepals, as well as the stel-
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