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In this article we will discuss about:- 1. Characters of Linaceae 2. Distribution of Linaceae 3. Economic Importance 4. Affinities 5. Important Type.
Characters of Linaceae:
Leaves simple, linear, alternate sometimes opposite; flowers actinomorphic, hypogynous, pentamerous; calyx and corolla 5 each, free petals usually contorted, clawed and fugacious, stamens 10, often 5 staminodes, inner connate forming a ring; carpels 2-5, synccospous, multilocalar, superior, axile placentation.
A. Vegetative characters:
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Habit:
Annual or perennial herbs, hook climbing shrubs or undershrub’s.
Root:
Tap and branched.
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Steem:
Erect, herbaceous, smooth.
Leaf:
Alternate, or rarely opposile, simple leaves of various forms-narrow, linear, linear-lanceolate; entire estipulate or stipulate-stipules fugacious caducous.
B. Floral characters:
Inflorescence:
Racemose or cymose, scorpioid (Flax), rarely solitary.
Flower:
Showy, actinomorphic, hermaphrodite, pentamerous, hypogynous.
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Calyx:
Sepals 5, polysepalous, or more or less connate, usually persistent, very rarely caduous, imbricate, quincunical, rarely valvate.
Corolla:
Petals 5, variously coloured, often more or less clawed, polypetalous, Fugucious, caducous, sometimes with ligule like appendages, usually with pocket like slits above the bases, imbricate or twisted.
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Androecium:
Stamens 10 usually, outer whorl being reduced to staminodes and inner one united at the base to form a ring, on the inner side of which is a disc or nector secreting glands, staminodes lie opposite to the petals; anthers elliptic, introrse, bithecal, connective often apically acute. Disc absent or interstaminal, free of adnate to staminal tube or extrastaminal forming a ring being united with the staminal tube.
Gynoecium:
Carpels 2-5, syncarpous, ovary superior, 2-5, syncarpous, ovary superior, 2-5 locular each locule further divided by false septum, so ovary cells or locules increased in number. Styles as many as ovary chambers or fewer or more free, axile placentation, ovules are 2 in each chamber; stigma terminal.
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Fruit:
Septicidal capsule, surrounded at the base by persistent calyx.
Seed:
Flat, shining, fleshy endosperm, sometimes with aril and winged appendages.
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Pollination:
Entomophilous, insects are attracted by coloured and honey glands.
Floral formula:
Distribution of Linaceae:
The family includes 22 genera and 200 species mainly distributed in the tropics of both the hemispheres.
Economic Importance of Linaceae:
1. Cattle feed:
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The oil-cake remaining after extraction of oil from seeds of L. Usitatissium is used as cattle feed.
2. Cloth:
The linen cloth is made from fibres, removed from the bast of the bark by a process of retting of Linum usitatissium and Reinwardita trigyna.
3. Gunny bags:
These are made from flax.
4. Linseed oil:
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It is obtained from seeds of Linum usitatissimum (H. Alsi). It is used in paints.
5. Timber:
Ctenolophon parviflorum (Malaya) yields a hard durable timber.
6. Ornamentals:
Linum perennae, L. grandiflora are cultivated as ornamentals.
Affinities of Linaceae:
Bessey, Rendle and Wettstein included it in Geraniales, Hallier transferred it to Guttales as a derivative from Ochnaceae and considered it as progenitor of several evolutionary lines including those giving rise to Sapotales, the Scrophulariaceae and others of the Tubiflorae, the Passiflorales, and probably the Polygalales.
Linaceae closely resembles Geraniceaeae and Malvaceae, so many taxonomists considered that this family was derived from the ancestor of Malvales.
Division of the family:
The family Linaceae is subdivided into two tribes:
I. Linoideae:
Stamens either isomerous or double the number of petals.
II. Ctenolophonioideae:
Stamens triple or more the number of petals.
Important Type of Linaceae:
Linum usitatissium (H. Alsi) (Fig. 44.1.):
Habit:
Annual cultivated herb.
Root:
Tap and branched.
Stem:
Erect, herbaceous, smooth and branched.
Leaf:
Simple, aternate, exstipulate linear, entire, narrow.
Inflorescence:
Cymose.
Flower:
Pedicellate, hermaphrodite, actinomorphic, hypogynous, blue or white bracteate.
Calyx:
Sepals 5, ovate acuminate, glandular, quincuncial.
Corolla:
Petals 5, polypetalous, clawed, aestivation-twisted.
Androecium:
Staamens 5, alternating with 5 staminodes, filaments connate at the base, nectar glands present; anther bithecous, introrse and versatile.
Gynoecium:
Carpels 5, syncarpous, ovary superior, axile placentation, stigma linear.
Fruit:
Specticial capsule.
Floral formula:
