Peyer patches are lymphoid nodules located in the walls of the small intestine.
Peyer patches are also known as aggregated lymphoid nodules, they are organized in the form of follicles and are round or oval and their surface is free of the villi and depressions that are present throughout the intestinal wall.
Peyer patches mainly consist of B cells and play an important part in the immune system by monitoring intestinal bacterial populations and controlling the development of pathogenic bacteria in the intestines.
Nitrogen fixation, N2 --> NH3+, is not something that plants to by themselves but some plants have bacteria that does this. I believe that pea plants have these, but I'm not 100% sure.
