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Imbricate: Overlapping like roofing shingles; in conifers, used for tightly pressed scale leaves of many Cupressaceae and Podocarpaceae.* The arborvitae (Thuja) above, a member of the Cupressaceae family, has imbricate …

Samara: A dry, indehiscent, winged fruit.* Tulip trees (Liriodendron tulipifera), maples (Acer spp.), and many other plants produce samaras, commonly referred to as ‘keys.’ Tulip trees, pictured above, often have whorls of …

Elaiosome (e-lay-o-zome): (Greek: elaion=oil + soma=body) literally meaning ‘oil body.’* A structure on the surface of a seed that secretes and stores oil, usually as an attractant to ants, which …

Hilum: The scar on a seed that marks the point at which it was attached to the plant.* Bean seeds have very obvious hilums. From left to right in the picture: …

Velamen: The thick sponge-like covering of the roots of epiphytic orchids which helps prevent water loss and aids in absorption.*   *Allikas, G. & Nash, N. (2000). Orchids. London: PRC.

Zygomorphic: Bilaterally symmetrical, so that a line drawn through the middle of the structure along only one plane will produce a mirror image on either side.* Orchid flowers are zygomorphic. …

Lenticel: A pore in the stem of a woody plant, showing as a raised spot that may be filled with a powdery substance. The pore permits air to reach tissues below …

Marcescent (mar-ses-ent): of parts of certain plants, remaining attached to the plant when withered.* Many oak (Quercus spp.) and beech (Fagus spp.) trees have marcescent leaves that persist well into the …

Pectinate: Arranged like the teeth of a comb; usually two-sided with respect to leaves.* Fir trees (Abies sp.) often show pectinate arrangement of their needles. *Eckenwalder, J.E. (2009). Conifers of the …