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Typical collen.
Developing collen.
Mature collen.
Thickened corners
Column in cortex
Nuclei
Lamellar, sparse
Lamellar, abundant
Pumpkin petiole
Birch petiole
Leaf vein
Leaf hypodermis

Fig. 4.1-4. Transverse section of stem of angelica. These are young collenchyma cells in which wall deposition in the corners has just begun. Once mature, they will be like the collenchyma in Fig. 4.1-1, which is the same species.