Narrow leaves have a parallel-vein pattern. Several large veins run alongside one another from the base of the blade to the tip. Small crossveins connect the large veins. Needle leaves are so small that they have only one or two veins running through the center of the blade. The Number of Blades per Leaf. A leaf with only one blade is called a simple leaf.
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Definition of vein. 1  1 : blood vessel; especially : any of the tubular branching vessels that carry blood from the capillaries toward the heart. 2  2a : any of the vascular bundles forming the framework of a leafb : any of the thickened cuticular ribs that serve to stiffen the wings of an insect.
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Definition of vein for Students. 1  1 : one of the blood vessels that carry the blood back to the heart. 2  2 : a long narrow opening in rock filled with a specific mineral a vein of gold. 3  3 : a streak of different color or texture (as in marble) 4  4 : a style of expression I continued in a more serious vein.
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The Blade, or lamina, is the broad, flat part of the leaf. Photosynthesis occurs in the blade, which has many green food-making cells. Leaf blades differ from one another in several ways: (1) the types of edges, (2) the patterns of the veins, and (3) the number of blades per leaf. The Types of Edges. Almost all narrow, grasslike leaves and needles leaves have a blade with a smooth edge, as do many broadleaf plants, particularly those that are native to warm climates.
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The Patterns of the Veins. Veins carry food and water in a leaf. They also support the blade, much as the metal ribs support the fabric of an open umbrella. In most broad leaves, the veins form a netlike pattern, with several large veins connected by smaller ones. The smallest veins supply every part of the blade with water.
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Quick Answer. Parallel venation refers to a pattern in the veins of a leaf where the secondary veins run parallel to each other off of a central, perpendicular primary vein. Parallel venation is also sometimes used to describe a similar pattern on an insect's wing. Venation is a general term for the pattern of veins on a leaf.
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1 : one of the blood vessels that carry the blood back to the heart. 2 : a long narrow opening in rock filled with a specific mineral a vein of gold. 3 : a streak of different color or texture (as in marble) 4 : a style of expression I continued in a more serious vein.
https://www.merriam-webster.com/dictionary/vein
Define vein: blood vessel; especially : any of the tubular branching vessels that carry blood from the capillaries toward the… — vein in a sentence blood vessel; especially : any of the tubular branching vessels that carry blood from the capillaries toward the heart…
https://www.merriam-webster.com/dictionary/vein
Pinnately veined leaves have one large central vein, called the midrib, which extends from the base of the blade to its tip. Other large veins branch off on each side of the midrib. The leaves of beech, birch, and elm trees have such a vein pattern.
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Definition of vein for English Language Learners. : 1  any one of the tubes that carry blood from parts of the body back to the heart. : 2  any one of the thin lines that can be seen on the surface of a leaf or on the wing of an insect. : 3  a long, narrow opening in rock filled with gold, silver, etc.
https://www.merriam-webster.com/dictionary/vein
what does the veins of a leaf do
Veins carry food and water in a leaf and support the blade.