They sound like Federal Status Codes used by the US Fish and Wildlife Service to define and rank rare plants. I remember there being catagories C1 through C3, but don't remember a C4. It has been a while since I have dealt with these rankings. I think C3 was plants no longer listed as endangered or threatened. There are also Global and State rankings that are widely used and developed by the Nature Conservancy. They would be G1, G2, G3, etc or S1, S2, S3 and so on. I think they both went up to 5 or 6. I could dig out my old files, which are at work, and list each plant with its various rankings but since these rankings can change over time you would want the most up to date list. The State office that handles this is the Office of Natural Lands Management, within the Division of Parks and Forestry. Again, I have their number at work, but I found the Division's main number in my phone book here at home. It is (609) 984-0370. They can connect you with Natural Lands Mgt., who should be able to send you a current list. Good luck!
