mesarchadj.

Brit.

/ˈmɛsɑːk/,

/ˈmɛzɑːk/, U.S.

/ˈmɛsɑrk/,

/ˈmɛzɑrk/

Origin: Partly a borrowing from German. Partly formed within English, by compounding. Etymons: German mesarch ; meso- comb. form, -arch comb. form².

Etymology: In sense 1 < German mesarch ( H. zu Solms-Laubach Einleitung in die Paläophytologie (1887) xi. 263) < meso- meso- comb. form + -arch -arch comb. form²; compare exarch adj. In sense 2 independently < meso- comb. form + -arch comb. form².

1. Botany. Of primary xylem: developing from both the centre of the stem and the periphery, so that the oldest elements (protoxylem) are in the centre of the xylem strand, and maturation of the cells takes place both centrifugally and centripetally.

ΘΚΠ

the world > plants > part of plant > cell or aggregate tissue > [adjective] > of xylem or phloem

reticulated1832

reticulate1842

concentric1878

interxylary1889

mesarch1891

hadrocentric1900

leptocentric1940

xylary1953

1891 H. E. F. Garnsey tr. H. zu Solms-Laubach Fossil Bot. xi. 257 Had he called..the leaf-strand of Cycadeae mesarch, and that of Isoëtes exarch.., we might..have been spared this misconception.

1911 Encycl. Brit. XXI. 735/2 When the protoxylems have an intermediate position the stele is mesarch (many Pterodophytes and some of the more primitive Phanerogams.)

1954 Biol. Rev. 29 63 Such studies resulted in the recognition of the now well-known centripetal and centrifugal patterns of differentiation, the exarch, endarch, and mesarch types of xylem.

1965 K. Esau Plant Anat. (ed. 2) xv. 378 In the third [type of xylem] the differentiation progresses in two or more directions from the first mature xylem elements. The resulting primary xylem is called mesarch.

1992 Rev. Palaeobot. & Palynol. 70 265/1 The xylem ring of the inner stele is mesarch, whereas the outer rings are exarch.

2. Ecology. Of a succession of plant communities: originating in a mesic or moderately moist habitat.

ΚΠ

1923 G. E. Nichols in Ecology 4 171 A third type [of succession] is here suggested, viz., mesarch... Mesarch series are those which originate in mesophytic habitats such as are afforded by moist, rich soils, and in which the vegetation likewise becomes progressively more and more advanced.

1960 N. Polunin Introd. Plant Geogr. xi. 324 They [sc. the seres] are distinguished as ‘hydrarch’, ‘mesarch’, or ‘xerarch’, according to whether their initiation is under damp, median, or dry conditions.

This entry has been updated (OED Third Edition, September 2001; most recently modified version published online March 2022).

单词	mesarch
释义	mesarchadj. Brit. /ˈmɛsɑːk/, /ˈmɛzɑːk/, U.S. /ˈmɛsɑrk/, /ˈmɛzɑrk/ Origin: Partly a borrowing from German. Partly formed within English, by compounding. Etymons: German mesarch ; meso- comb. form, -arch comb. form². Etymology: In sense 1 < German mesarch ( H. zu Solms-Laubach Einleitung in die Paläophytologie (1887) xi. 263) < meso- meso- comb. form + -arch -arch comb. form²; compare exarch adj. In sense 2 independently < meso- comb. form + -arch comb. form². 1. Botany. Of primary xylem: developing from both the centre of the stem and the periphery, so that the oldest elements (protoxylem) are in the centre of the xylem strand, and maturation of the cells takes place both centrifugally and centripetally. ΘΚΠ the world > plants > part of plant > cell or aggregate tissue > [adjective] > of xylem or phloem reticulated1832 reticulate1842 concentric1878 interxylary1889 mesarch1891 hadrocentric1900 leptocentric1940 xylary1953 1891 H. E. F. Garnsey tr. H. zu Solms-Laubach Fossil Bot. xi. 257 Had he called..the leaf-strand of Cycadeae mesarch, and that of Isoëtes exarch.., we might..have been spared this misconception. 1911 Encycl. Brit. XXI. 735/2 When the protoxylems have an intermediate position the stele is mesarch (many Pterodophytes and some of the more primitive Phanerogams.) 1954 Biol. Rev. 29 63 Such studies resulted in the recognition of the now well-known centripetal and centrifugal patterns of differentiation, the exarch, endarch, and mesarch types of xylem. 1965 K. Esau Plant Anat. (ed. 2) xv. 378 In the third [type of xylem] the differentiation progresses in two or more directions from the first mature xylem elements. The resulting primary xylem is called mesarch. 1992 Rev. Palaeobot. & Palynol. 70 265/1 The xylem ring of the inner stele is mesarch, whereas the outer rings are exarch. 2. Ecology. Of a succession of plant communities: originating in a mesic or moderately moist habitat. ΚΠ 1923 G. E. Nichols in Ecology 4 171 A third type [of succession] is here suggested, viz., mesarch... Mesarch series are those which originate in mesophytic habitats such as are afforded by moist, rich soils, and in which the vegetation likewise becomes progressively more and more advanced. 1960 N. Polunin Introd. Plant Geogr. xi. 324 They [sc. the seres] are distinguished as ‘hydrarch’, ‘mesarch’, or ‘xerarch’, according to whether their initiation is under damp, median, or dry conditions. This entry has been updated (OED Third Edition, September 2001; most recently modified version published online March 2022). < adj.1891
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