Page 1 : 2) Hypodermis is sclerenchymatus., 3) Vascular bundles are numerous —, , , , 3) Vascular bundles are limited in number, , , , , ‘and are arranged in the form of a broken ring and are scattered in the ground tissue., 4) Vascular bundles are conjoint, collateral 4) V.B are conjoint collateral and closed., & open., , , , , Secondary growth of dicot stem., , The increase in girth or thickness of the axis (ster/root) is called secondary growth. In dicot stem, secondary growth takes place by the activity of two cambial rings called vascular cambium and cork, cambium.(lateral meristems) In dicot stem secondary growth takes place in two stages, , , , , 4 Stelar secondary growth 2 cortical secondary growth., , , , Stelar secondary growth ~involves two process, (a) Formation of vascular cambium, , The cambium present in the primary vascular bundle is called intrafascicular cambium. The cells of, medullary rays, adjoining these intafascicular cambium becomes meristematic and from the interfascicular, cambium, This interfascicular and interfascicular cambium joins to form a complete ring of vascular cambium., , (b) Activity of vascular cambium, , The vascular cambium consists of two types of cells fusiform initials and ray initials. Fusiform initials, produce, secondary, xylem towards inside and secondary phloem towards outside. Ray initials produces, secondary medullary rays towards both the sides. Fusiform initials are more active towards inside, so more, secondary xylem is produced, than the secondary phloem. The primary and secondary phloem gets gradually, crushed due to the continued formation and accumulation of secondary xylem., , The secondary xylem is composed of tracheids, vessels, xylem fibers and xylem parenchyma,, Secondary xylem represents the wood of dicot stem. Mechanical support and upward conduction are the chief, function of secondary wood. The main function of secondary phloem is the translocation of food materials., , Formation of secondary vascular tissues in the stele exerts a great pressure on the cortex and, epidermis. In order to replace the damages occurred in the cortical region as a result of stellar secondary, , growth, cortical secondary growth takes place., , Cortical Secondary Growth or Extra Stelar Secondary Growth — Which involves two process.