Several different types of tissues form the structures of the lymphatic system. Which of the following lymphoid tissue is unencapsulated?

The respiratory, alimentary and genitourinary tracts are guarded immunologically by subepithelial accumulations of lymphoid tissues which are not constrained by a connective tissue capsule. These may occur as diffuse collections of lymphocytes, plasma cells and phagocytes throughout the body and the lamina propria of the intestinal wall, or as more clearly organized tissue with well-formed follicles as found in the Peyer's patches.