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.
There are two major types of mesophyll material found within leaves. These types are formed in distinct layers within the leaf. The first of these two layers, which lies on the outside close to the epidermis, is referred to as the palisade layer.The palisade layer of mesophyll is comprised of tightly packed cells containing many chloroplasts.The second subtype, the so-called spongy layer, is a less densely packed material with a great deal of air in-between cells. It also contains far less chloroplasts than the other type of mesophyll.hese types are formed in distinct layers within the leaf. The first of these two layers, which lies on the outside close to the epidermis, is referred to as the palisade layer. The palisade layer of mesophyll is comprised of tightly packed cells containing many chloroplasts.