Final answer:
The provided materials do not clearly specify which Gmelin or work is being referenced, which prohibits an accurate response to the question about the most notable part of Gmelin's work.
Step-by-step explanation:
The most notable part of Gmelin's work is not clearly defined in the provided reference material, which mentions several individuals but doesn't specify which accomplishments of a person named Gmelin are to be addressed. If we're considering historical figures, Johann Georg Gmelin might be inferred, known for his exploratory work in Siberia and contributions to botany and chemistry during the 1730s. However, since the references provided don't align with a particular Gmelin's contributions, we cannot determine the exact notable work without further context or information. This illustrates the importance of providing clear and specific questions to avoid ambiguity in educational settings.