Flowering plant serve to protect the sporophylls and to form an envelope attractive to pollinators. The individual members of these surrounding structures are known as sepals and petals (or tepals in flowers such as "Magnolia" where sepals and petals are not distinguishable from each other). The outer series (calyx of sepals) is usually green and leaf-like, and functions to protect the rest of the flower, especially the bud. The inner series (corolla of petals) is, in general, white or brightly colored, and is more delicate in structure. It functions to attract insect or bird pollinators. Attraction is effected by color, scent, and
Surround channels strictly diffuse. Optimally there should be discrete surround channels for diffuse and direct effects. This is part of the design for Tomlinson Holman's 10.2 surround sound. For movies surround channel information is usually more diffuse ambient noise. Some surround sound systems such as Dolby Digital EX and Pro Logic IIx incorporate a third (back surround) or even fourth surround channel (back left and back right). These channels are "matrixed" from the standard surround channels; they are not discrete. Some matrix encoding surround sound systems use a single back center channel surround (Dolby Digital EX, Dolby Pro Logic IIx 6.1) or