Fascicle (botany)

In botany, a fascicle is a bundle of leaves or flowers growing crowded together; alternatively the term might refer to the vascular tissues that supply such an organ with nutrients. However, vascular tissues may occur in fascicles even when the organs they supply are not fascicled. In zoology and animal anatomy the term fascicle refers to a small bundle, usually of fibres, nerves, or vessels.

The term fascicle and its derived terms such as fasciculation are from the Latin fasciculus, the diminutive of fascis, a bundle. Accordingly such words occur in many forms and contexts wherever they are convenient for descriptive purposes. A fascicle may be leaves or flowers on a short shoot where the nodes of a shoot are crowded without clear internodes, such as in species of Pinus or Rhigozum. However, bundled fibres, nerves or bristles as in tissues or the glochid fascicles of Opuntia may have little or nothing to do with branch morphology.

Leaf fascicles are present in all pines, and the number of adult leaves (needles) per fascicle is an important character for identification of pine species and genera. Most species have fascicles of 2 to 5 needles; only occasional species typically have as few as one or as many as six leaves to the fascicle.

Variation is high between species, low within them. For example, Pinus flexilis (limber pine), has fascicles of 5 needles. This pine is a member of the white pine group, Pinus subgenus Strobus, section Strobus. In all members of the group the fascicles nearly all have five needles and the sheath at the base of the fascicle is deciduous.

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