Step 1: Understanding the Question:
We need to name the crude drug source that yields chikusetsu saponins.
Step 2: Key Concept:
Chikusetsu saponins belong to the dammarane type triterpene saponin group, the same chemical class as the ginsenosides found in ginseng.
Step 3: Detailed Explanation:
Panax japonicus, called chikusetsu ninjin, is the direct source plant, and it sits in the Panax genus alongside Panax ginseng, so texts group chikusetsu saponin under the ginseng drugs. Senega, Quillaja, and liquorice each carry structurally distinct saponin classes, senegins, quillaja saponins, and glycyrrhizin, that don't belong to this dammarane group at all.
Step 4: Final Answer:
Ginseng.