What is :
Phellogen
Hypodermis
Phellogen is a meristem (tissue where cell division occurs) layer of the plant that gives rise to the formation of the protective bark on stems and roots.
Hypodermis is the layer of cells immediately beneath the epidermis (outermost layer of cells) of a plant, providing structural support and regulating the movement of water and nutrients.
1. Phellogen, also known as the cork cambium, is a layer of cells found in the outermost layer of stems and roots of plants. It is responsible for producing the outer bark of woody plants. The phellogen cells divide to produce new cells both inwardly, toward the central part of the plant, and outwardly, toward the surface. The cells produced inwardly become phelloderm, which is a relatively thin layer of cells, while the cells produced outwardly become the cork cells that make up the protective outer layer of bark.
2. The hypodermis, in animals, refers to the layer of tissue located beneath the epidermis, which is the outermost layer of the skin. The hypodermis is primarily composed of fat cells (adipocytes) and connective tissue. It acts as an insulating layer, helping to regulate body temperature, and also provides shock absorption and cushioning for the organs and tissues beneath it. In addition, the hypodermis is involved in storing energy in the form of fat.