Bracts and involucres

 Bracts may occur within an inflorescence or below an inflorescence. The term "bract" refers to a reduced or scale-like leaf that is associated with a flower or inflorescence. Bracts may subtend individual flowers, branches in an inflorescence, or the entire inflorescence.

Sometimes it is difficult to tell whether to classify a leaf as a regular foliage leaf or as a bract. This is particulary true when trying to determine whether a plant has solitary axillary flowers or a bracted raceme:

Bracted raceme vs solitary axillary flowers
Where leaves that subtend individual flowers are indistinguishable from regular foliage leaves, the flowers are usually considered solitary. Where flowers are subtended by much-reduced leaf-like structures, those structures are generally considered bracts within a multi-flowered inflorescence.

 Some bracts occur in groups at the base of an entire inflorescence. These bracts may make up a structure called an involucre.

Umbel with involucre
This is an umbel subtended by bracts that make up an involucre.

 In the Asteraceae (the sunflower family), flowers occur in heads. Each head has an involucre, and the bracts of the involucre are called phyllaries.

Sunflower head with phyllaries
A sunflower head with an involucre that is composed of numerous phyllaries. These phyllaries are not part of any individual flower.

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