Which plant is a source of cardiac glycosides and has historical significance in treating heart conditions?

Foxglove is well-known as a source of cardiac glycosides, particularly a compound called digoxin, which has been used in the treatment of various heart conditions, including heart failure and atrial fibrillation. The plant's historical significance dates back to the 19th century when it was popularized for its medicinal properties and has been integral in developing modern pharmacology related to cardiac health. The glycosides found in foxglove work by increasing the force of heart contractions and regulating heart rhythm, highlighting the plant's importance in both traditional and contemporary medicine.

In contrast, Aloe Vera is primarily used for its soothing properties for skin ailments and digestive health, while Cassava is a significant food source but is not associated with cardiac glycosides. Ginger is primarily known for its anti-inflammatory and digestive benefits. Thus, the unique role of foxglove in cardiac medicine sets it apart as the correct answer regarding the therapeutic use of glycosides.