from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun An enveloping sheath or envelope, such as the sheath of new bone that forms around a sequestrum.
from The Century Dictionary.
- noun In pathology, a wall of new osseous tissue inclosing the sequestrum in a case of necrosis.
- noun In zoology, a kind of sheath or involucre about the bases of the thread-cells of acalephs.
- noun In botany: Same as
- noun Same as
from the GNU version of the Collaborative International Dictionary of English.
- noun (Bot.) See
- noun (Zoöl.) A sheath which surrounds the base of the lasso cells in the Siphonophora.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun A
sheaththat coversor envelopes, especially one that forms around the sequestrumof new bone
from The American Heritage® Dictionary of the English Language, 4th Edition
-- This is no discovery of criticism; -- it is a necessity of the human mind; and all nations have felt and obeyed it, in the invention of metre, and measured sounds, as the vehicle and 'involucrum' of poetry -- itself a fellow-growth from the same life, -- even as the bark is to the tree!
A little later the involucrum becomes developed, and is no unimportant feature.
The leaves are triternate, divisions deeply cut and acute; the leaves of the involucrum are stalked, trifid, and deeply cut.
Said involucrum is composed of numerous small leaves, a distinguishing trait from its nearest relative genus _Rudbeckia_.
It belongs to that section of its numerous genus having an involucrum of stalked leaflets.
The double involucrum, common to the genus, has its upper set of bracteoles rolled outward; they are of a brownish colour; the lower set are green and wheel-shaped during the period of a perfect ray, and they alternate with the upper ones.
Tagetes, _Sud Buruk_, is a curious genus, on account of its simple tubular involucrum, very entire and pappus florets, conduplicate in aestivation, all florets faeminine are ligulate; are the folded up ones representations of the males?
The pure white flower -- more than an inch across -- is somewhat distant from the handsome three-leaved involucrum, and is supported by a wiry flower stalk, 3in. to 5in. long; it is about the same length from the root, otherwise the plant is stemless.
Curious transformation in Carthamus was observed, either affecting the involucrum alone, when those branches that would have become flowers become clavate, covered with very dense aristate leaves, or affecting the florets which become more or less converted in the branches.
The flowers are borne at the height of 2ft. to 3ft., and are produced singly on very thick, rigid stalks, long, nearly nude, grooved, furnished with numerous short, bristle-like hairs, and gradually thickening up to the involucrum of the flower.