PRIMARY AND SECONDARY PLANT GROWTH Page 3

• II. Secondary Growth
• B. Cork Cambium
• 
• 1. Origin is discontinuous in space and time
• a. Initial Cork Cambium derived from Epidermis or Cortex
• 
• b. New Cork Cambium made each year to inside of old Cork Cambium
• c. Subsequent Cork Cambium derived from parenchyma in Primary and Secondary Phloem
• 2. Cork Cambium makes Cork Cells toward outside
• 3. Because of discontinuity Bark can include:
• a. Epidermis + Cortex
• b. Non Functional Primary Phloem
• c. Non Functional Secondary Phloem
• 4. Can be sloughed off, or accumulated into thick ridges & furrows
• 
• 5. Special regions of loose cork cells (Lenticels) are produced to facilitate gaseous exchange from atmosphere to internal living cells.
• 
• 6.  Human uses of Bark
• a.  Source of Tannic Acid used in making leather
• b.  Source of Cinnamon, one of the oldest and most valuable spices known
• c.  Phloem Fibers from
• 1. Flax used to make Linen cloth
• 2. Hemp used to make Hemp cloth, canvas, cordage
• 3. Jute used to make Burlap
• d.  Landscape Mulch
• e.  Fuel
• Page 1 2