Basic morphology: The vegetative body (thallus) of a filamentous mold is primarily composed of what structure?

Introduction / Context:
Understanding fungal anatomy helps interpret culture plates and microscopic mounts. The vegetative thallus provides growth and nutrient acquisition.

Given Data / Assumptions:

• Molds grow as filaments called hyphae.
• A mass of hyphae is termed a mycelium.
• Spores are reproductive, not the vegetative body.

Concept / Approach:
The thallus of molds is the network of hyphae forming the mycelium. While spores may be present, they are structures for reproduction and dissemination rather than the main vegetative mass.

Step-by-Step Solution:
Identify vegetative vs. reproductive structures. Assign “mycelium” to vegetative thallus. Exclude spores as the primary thallus component. Choose “mycelium.”

Verification / Alternative check:
Microscopy of lactophenol cotton blue mounts shows branching hyphae forming the bulk of the organism.

Why Other Options Are Wrong:

• Spores: Reproductive units, not the vegetative mass.
• Both/None/Sclerotia only: Overgeneralizations or incorrect specificity.

Common Pitfalls:
Confusing abundant conidia on aerial hyphae with the vegetative body itself.

Final Answer:
mycelium.