A DID system can be used for fax and voice mail as well as for live voice connections. Compared to regular PBX service, DID saves the cost of a switchboard operator, calls go through faster, and callers feel they are calling a person rather than a company.
Key Concepts: In dicotyledonous leaves there are two types of mesophyll cells, palisade mesophyll and spongy mesophyll. Palisade mesophyll cells form a layer beneath the upper epidermis whereas spongy mesophyll cells are internal to the lower epidermis.
The mesophyll is the main inner leaf tissue making up the blade of the leaf. Most of the photosynthesis of the plant takes place in the mesophyll. The mesophyll in the upper part of the leaf is made up of tightly packed cells, full of chloroplasts, and is called the palisades layer.The mesophyll in the lower part of the leaves is made up of loosely packed cells and is called the spongy layer.The vascular tissue functions like the circulatory system of the plant. The xylem carries water from the roots to the leaves and to the other upper parts of the plant.he mesophyll in the lower part of the leaves is made up of loosely packed cells and is called the spongy layer. The vascular tissue functions like the circulatory system of the plant. The xylem carries water from the roots to the leaves and to the other upper parts of the plant.