Venation Patterns

leaf clearing
This is a clearing of the tip of one tomato leaf. Note the complex network of vascular bundles.
leaf clearing (v-midvein, a-areole, t-trichome)	leaf clearing (t-trichome)
The clearing on the left shows a closer view of the venation pattern. Notice that many of the veins form boxes called areoles. The clearing on the right shows the numerous trichomes found on tomato leaves.
leaf clearing (x-xylem)	leaf clearing
This leaf's xylem vessels are mostly composed of protoxylem. The secondary wall of these vessel members forms helical thickenings. The helical thickenings allow for more growth and expansion. This pattern of secondary wall thickening is typical of rapidly expanding vessels.

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