What is Digitalis derived from?

Digitalis is a medication that is derived from the foxglove plant, specifically from the leaves. The active compounds in Digitalis, known as cardiac glycosides, are used to treat heart conditions by increasing the force of heart contractions and regulating heart rate. The foxglove, particularly species like Digitalis purpurea, has been historically significant in medicine for its effects on the cardiovascular system.

The other options do not provide such medicinal benefits. Cacti are primarily known for their ability to store water and survive in arid environments. Willow trees are often associated with their use in traditional medicine for pain relief because they contain salicylic acid, which is a precursor to aspirin, but they do not produce Digitalis. Corn plants are agricultural crops and do not have a connection to the heart-related properties of Digitalis. Thus, foxgloves are the correct source for this important cardiac medication.