Here is an essay on the ‘Lamina of a Leaf’ for class 9, 10, 11 and 12. Find paragraphs, long and short essays on the ‘Lamina of a Leaf’ especially written for school and college students.
Essay # 1. Shape of Lamina:
The lamina shows much variation with regard to their shapes.
These are divided into three main groups:
a. Lamina with almost same width throughout.
Lamina is needle-shaped, long, thin and pointed, e.g., Pinus sp. (Fig. 2.62A).
Lamina is long and very narrow with nearly parallel margins, e.g., tube-rose, Polyanthes tuberosa, rice, wheat and in many grasses (Fig. 2.62B).
b. Lamina with widest middle.
Lamina is broadest in the middle or a little below and tapering towards both the ends, e.g., oleander, Nerium indicum (Fig. 2.62C) of Apocynaceae, Polygonum orientate of Polygonaceae, Butomopsis lanceolata of Alismataceae etc.
Lamina is almost rectangular i.e., flat and broad with a round apex, e.g., banana, Musa paradisiaca of Musaceae (Fig. 2.62D) etc.
c. Lamina with widest base.
5. Subulate or Awl-Shaped:
Lamina is long and narrow, tapering gradually from base to apex, e.g., saltwort, Salsola kali of Chenopodiaceae; Isoetes (Fig. 2.62E), a pteridophyte.
6. Ovate or Egg-Shaped:
Base of lamina is wider than the apex, e.g., banyan, Ficus benghalensis of Moraceae; Solanum nigrum of Solanaceae; china-rose, Hibiscus rosa-sinensis (Fig. 2.62F) etc.
Lamina is heart-shaped, i.e., its base is broad and lobed and has a pointed apex, e.g., betel vine, Piper betel (Fig. 2.62G) of Piperaceae; Sida cordifolia and Abutilon indicum of Malvaceae etc.
Lamina is arrow-shaped i.e., two lower lobes, one on each side pointing downwards, e.g., Sagittaria sagittifolia (Fig. 2.62H) of Alismataceae; Ipomoea aquatica of Convolvulaceae etc.
Lamina is arrow-shaped, but the two lower lobes are directed outwards, e.g., Ipomoea sp. (Fig. 2.62I) of Convolvulaceae; Typhonium trilobatum of Araceae.
10. Reniform or Kidney-Shaped:
Lamina is rounded above with a deep notch at its base, e.g., Indian pennywort, Centella asiatica (Fig. 2.62J) of Apiaceae.
Lamina is like a half-moon with pointed basal lobes i.e., semicircular in outline, e.g., Adiantum lunatum, a pteridophyte; Passiflora lunata (Fig. 2.62K) of Passifloraceae etc.
d. Lamina with widest apex.
Lamina is like an inverted egg (reverse of ovate), e.g., jack, Artocarpus heterophyllus (Fig. 2.62L) of Moraceae; Cassia obovata of Fabaceae etc.
Lamina is like an inverted heart i.e., its apical region is broad and bilobed, e.g., Bauhinia variegata (Fig. 2.62M) of Fabaceae; Oxalis corniculata of Oxalidaceae etc.
14. Spathulate or Spathula-Shaped:
Lamina is broad and rounded at the apex and gradually tapers towards the base, e.g., Phyla nodiflora (Fig. 2.62N) and Duranta repens of Verbenaceae; Drosera burmanii of Droseraceae etc.
15. Cuneate or Wedge-Shaped:
Lamina looks like the hood of a snake i.e., its breadth increases towards the apex, e.g., water lettuce, Pistia stratiotes (Fig. 2.62O) of Araceae.
16. Lyrate or Lyre-Shaped:
Lamina looks like a lyre having a large oval terminal lobe and two or more smaller lobes, e.g., radish, Raphanus sativus and mustard, Brassica nigra (Fig. 2.62P) of Brassicaceae.
e. Lamina symmetrical.
17. Elliptical or Oval:
Lamina is like an ellipse, e.g., Indian rubber, Ficus elastica of Moraceae; guava, Psidium guajava of Myrtaceae (Fig. 2.62Q) etc.
18. Orbicular (Circular) or Rotund or Peltiform:
Lamina is circular and petiole is attached below the centre and the leaf looks like an umbrella, e.g., lotus, Nelumbo nucifera (Fig. 2.62R) of Nymphaeaceae etc.
Essay # 2. Base of Lamina:
The base of lamina is of different types:
Leaf-bases of the sessile leaves form two lobes like that of wings, which partially surround the stem, e.g., Mexican poppy, Argemone mexicana of Papaveraceae, Calotropis procera (Fig. 2.63A) of Asclepiadaceae etc.
Lobes of sessile leaf become fused together; thereby the leaf completely surrounds the stem, e.g., Canscora perfoliata (Fig. 2.63B) of Gentianaceae, Aloe perfoliata of Liliaceae etc.
Bases of two sessile leaves with opposite phyllotaxy are completely fused together, e.g., Canscora diffusa (Fig. 2.63C) and Swertia chirata of Gentianaceae etc.
Leaf base is winged and fused with the stem, e.g., Laggera alata and Sphaeranthus indicus (Fig. 2.63D) of Asteraceae.
Essay # 3. Surface of Lamina:
The surface of lamina is of different types:
Surface of lamina is smooth and free from hairs, e.g., Pongamia glabra of Fabaceae; pink, Dianthus chinensis of Caryophyllaceae.
Surface of lamina has a coating of wax and appears to be shiny, e.g., Solanum glaucum of Solanaceae.
Surface of lamina becomes sticky due to some sugary exudation, e.g., Cleome viscosa and Polanisia icosandra of Capparidaceae.
Surface of lamina is rough due to some short rigid points, e.g., Ficus hispida of Moraceae.
Surface of lamina is somewhat wrinkled, e.g., Rubus rugosus of Rosaceae.
Surface of lamina becomes covered with glands, e.g., lemon, C. aurantifolia of Rutaceae.
Surface of lamina becomes covered with hairs.
These are of the following types:
Covered with long, soft and scattered hairs, e.g., Grewia flavescens of Tiliaceae.
Covered with long, rigid scattered hairs, e.g., Cucurbits.
Covered with stiff, fine and scattered hairs, e.g., Eclipta alba of Asteraceae.
Covered with short, dense and cottony hairs, e.g., Calotropis procera of Asclepiadaceae, Guazuma tomentosa of Sterculiaceae etc.
Covered with long and interwoven hairs like wool, e.g., Solarium verbescifolium of Solanaceae.
Surface of lamina is overed with prickles. e.g., Hibiscus esculentus of Malvaceae.
Essay # 4. Margin of Lamina:
The margin of the lamina may be of the following types:
Margin is smooth i.e., without indentations (Fig. 2.64A), e.g., mango, Mangifera indica; banyan, Ficus benghalensis.
Margin is wavy with indentations < 1/16 distance to midrib (Fig. 2.64B), e.g., Polyalthia longifolia of Annonaceae.
Margin is like the teeth of a saw, pointed upwards (Fig. 2.64C), e.g., china- rose, Hibiscus rosa-sinensis.
Margin is toothed but the teeth again become serrated (Fig. 2.64D), e.g., elm tree.
Margin is toothed and pointed downwards (Fig. 2.64E).
Margin is toothed and the teeth are pointed outward at right angles to midrib (Fig. 2.64F), e.g., water-lily.
Margin is toothed and the teeth are again dentate (Fig. 2.64G).
Margin is toothed and the teeth are rounded (Fig. 2.64H), e.g., Centella asiatica of Apiaceae.
Margin is toothed and the teeth are crenate (Fig. 2.64I).
Margin is toothed and the teeth are pointed to form spines (Fig. 2.64J), e.g., Mexican poppy, Argemone mexicana of Papaveraceae; Solanum xanthocarpum of Solanaceae.
11. Incised or Lobed:
Margin is incised into various depths and divided into small lobes (Fig. 2.64K), e.g., mustard, Brassica nigra; radish, Raphanus sativa etc.
Essay # 5. Apex of Lamina:
The apex of lamina is of the following types:
Apex is pointed forming a terminal angle of 45°-90°, e.g., mango, Mangifera indicia (Fig. 2.65A); china-rose, Hibiscus rosa-sinensis etc.
Apex is slender and much prolonged like a tapering tail forming a terminal angle of < 45°, e.g., peepul tree, Ficus religiosa (Fig. 2.65B) of Moraceae, Bauhinia acuminata of Fabaceae (Caesalpiniaceae).
Apex is broad angled (>90°) and blunt, e.g., banyan, Ficus benghalensis (Fig. 2.65C).
Apex is as broad as or broader than long and forms a sharp point, e.g., Catharanthus roseus (Fig. 2.65D) of Apocynaceae.
5. Cuspidate or Spiny:
Apex ends in a hard and pointed structure, e.g., date palm, Phoenix sylvestris (Fig. 2.65E) of Arecaceae, Agave cantula of Agavaceae etc.
Apex becomes narrowed and forms a tendril, e.g., glory lily, Gloriosa superba (Fig. 2.65F) of Liliaceae.
Apex ends in a fine thread-like coiled or flexuous structure, e.g., banana, Musa paradisiaca (Fig. 2.65G) of Musaceae.
Apex is cut across abruptly, almost at right angle to midrib, e.g., Indigofera linifolia of Fabaceae, Paris polyphylla (Fig. 2.65H) of Liliaceae etc.
Obtuse apex is slightly notched, e.g., Clitorea ternatea of Fabaceae, water lettuce, Pistia stratiotes (Fig. 2.65I) of Araceae etc.
Obtuse apex is deeply notched, e.g., Bauhinia variegata (Fig. 2.65J) of Fabaceae.
Essay # 6. Texture of Lamina:
Lamina is thick and leathery, e.g., mango, Mangifera indica; Indian rubber, Ficus elastica; Vanda roxburghii and Vanilla planifolia of Orchidaceae.
Lamina is thin and membranous, e.g., china-rose, Hibiscus rosasinensis; rose, Rosa centifolia etc.
Lamina is fleshy and more or less brittle, e.g., Aloe indica of Liliaceae, Bryophyllum calycinum of Crassulaceae.
4. Gland-Dotted or Glandular:
Lamina is dotted with glands and the glands are filled with essential oil, e.g., lemon, Citrus limon of Rutaceae; custard apple, Annona squamosa of Annonaceae.