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 palisade mesophyll tissue is a layer of cells in a leaf. These cells all contain numerous chloroplasts, which contain the green chemical required for photosynthesis. At the top of the slide you can also see some epidermal cells. These do NOT contain chloroplasts.