Definition of "involucrum" [‖In•vo•lu•crum]

• An enveloping sheath or envelope. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "-- 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!"
• "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?"
• "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."