Historical concepts of the velamen and exodermis are reviewed. Twenty species and hybrids representing 13 genera of orchids were investigated to determine the origins of the velamen and exodermis. 14 orchid root tips belong to the category of histogens known as Type I; the other 6 root tips belong to Haberlandt''s Type VI. The velamen is derived from the protoderm; it is a multiple epidermis. The exodermis is the specialized outermost layer of the cortex, and corresponds, in its limiting position, and its similar ontogeny, to the endodermis.