Q.Explain the internal structure of Cycas rachis.

Step 1. In transverse section, the outermost layer of the Cycas rachis is a single-layered epidermis covered by a thick cuticle.

Step 2. Just beneath the epidermis is the hypodermis, made of sclerenchyma — two layers thick on the adaxial (upper) side but many layers thick on the abaxial (lower) side, giving mechanical support.

Step 3. The bulk of the rachis interior is parenchymatous ground tissue.

Step 4. The most distinctive feature is the arrangement of the vascular bundles: rather than sitting in a simple ring, they are arranged in a characteristic inverted omega (Ω) shape. Each individual bundle is wrapped in its own single-layered sclerenchymatous bundle sheath, is surrounded by a single-layered endodermis and a few-layered pericycle, and shows a diploxylic condition — meaning xylem is present on both …

Work through the rachis cross-section layer by layer from epidermis inward, ending on the …

• Describing the rachis anatomy as identical to the Cycas stem, when the rachis's inverted-omega, diploxylic vascular arrangement is a distinct and unique feature. …