The filbert, 2 among the numerous varieties of Corylus Avellana, is extensively cultivated, especially in Kent, for the sake of its nuts, which are readily distinguished from cob-nuts by their ample involucre and greater length.
In Compositae the name involucre is applied to the bracts surrounding the head FIG.
The seeds, or properly fruits, are contained singly in a stony involucre or bract, which does not open until the enclosed seed germinates.
This involucre is frequently composed of several rows of leaflets, which are either of the same or of different forms and lengths, and often lie over each other in an imbricated manner.
The leaves of the involucre are spiny in thistles and in teazel (Dipsacus), and hooked in burdock.
The cup-shaped involucre of Cornucopia is a dilatation of the axis into a hollow receptacle with a raised border.
The young involucre surrounds the female flower and the stalk supporting the spike of male flowers, and when ripe has the appearance of bluish-white porcelain.
In Cynosurus (Dog's tail) -- C the pectinate involucre which conceals the spikelet is a barren or abortive spikelet.
In Setaria and allied genera the spikelet is subtended by an involucre of bristles or spines which represent sterile branches of the inflorescence.
In Compositae besides the involucre there are frequently chaffy and setose bracts at the base of each flower, and in Dipsacaceae a membranous tube surrounds each flower.