mesarch


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mesarch

[′me‚zärk]
(botany)
Having metaxylem on both sides of the protoxylem in a siphonostele.
(ecology)
Originating in a mesic environment.
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The primary vasculature is non-sympodial, and primary xylem only occurs as the downward extension of mesarch leaf traces (Fig.
Mesarch joined the firm in 1998 and specializes in trust taxation and complex corporate and individual tax matters.
Eleven character states change on the branch subtending Biscalitheca + Corynepteris: #5, growth form of stem/axis erect [right arrow] rhizomatous; #7, arborescence present [right arrow] absent; #24, scales absent [right arrow] present; #35, protoxylem of stem/axis mesarch [right arrow] exarch; #41, radial rachis/axis trace round-elliptical [right arrow] absent; #57, meio/microsporangium bearing structure unlike vegetative [right arrow] somewhat modified from the vegetative; #61, abaxially attached sporangia absent [right arrow] present; #65, meio/microsporangial grouping absent [right arrow] present; #71, sporangial stalk absent [right arrow] broad; #74, functional annulus absent [right arrow] present; and #88, exospore surface nearly smooth or plain [right arrow] obviously sculptured.
Among the fossil forms, Fascivarioxylon (Jain, 1962), of the Jurassic of India, has a vascular cylinder with mesarch, bicollateral centrifugal-centripetal bundles, with uniform secondary growth in both directions; and Stem B, found in the Argentinian Cretaceous, has inverse bundles inside the first vascular cylinder.