WB01705.gif (1157 bytes)  Xylem-2  WB01704_.gif (383 bytes)

Eustele-1240Lab.jpg (64457 bytes) Aristolochia Stem Cross-Section: Note the arrangement of Vascular Bundles in this low magnification image. This is typical for Dicots.
AriStmXS2TBLab300.jpg (36181 bytes)
Cross-section of Aristolochia stained with Toluidine Blue
Tracheary Elements have thick Secondary cell walls which are heavily Lignified. The specimen on the left is from the tropical vine Aristolochia. It has been stained with Toluidine Blue which stains lignified walls Blue. The xylem is contained within the circle. What else has stained positively for lignin in this slide?
aristl-1-300.jpg (16499 bytes) This specimen was stained with Phloroglucinol which stains lignin red. Note the ring of extraxylary (Bast) fibers that encircles the stem in the Cortex.
aristl-2-pol300.jpg (13438 bytes) This is the same specimen as above viewed with Polarized Light. The thick walls of the tracheary elements and sclerenchyma in the Xylem are birefringent. The extraxylary  fibers are also birefringent.
arlflwer.jpg (26847 bytes) Aristolochia Flower in face view. This is called Dutchman's pipe because of its shape in side view. It has an interesting pollination biology.
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