| Id. | Gruppe | Links |
| 51 | Cactaceae | |
| 105 | Cadmium | |
| 106 | Caesium | |
| 62 | Calcium | |
| 231 | Campanulaceae | |
| 111 | Canidae | |
| 112 | Cannabaceae | |
| 113 | Cannaceae | |
| 232 | Caprifoliaceae | |
| 10 | Carbonium | |
| 25 | Caryophyllaceae | |
| 176 | Celastraceae | |
| 125 | Cervidae | |
| 178 | Chactidae | |
| 77 | Chenopodiaceae | |
| 39 | Chlorum | |
| 131 | Chromium | |
| 226 | Chrysomelidae | |
| 201 | Cistaceae | |
| 134 | Cladoniaceae | |
| 135 | Clavicipitaceae | |
| 98 | Clostridiaceae | |
| 192 | Clusiaceae | |
| 136 | Cobaltum | |
| 155 | Coccidae | |
| 138 | Coccinellidae | |
| 323 | Commelinaceae | |
| 141 | Convolvulaceae | |
| 142 | Corallidae | |
| 144 | Coriariaceae | |
| 145 | Cornaceae | |
| 162 | Corynebacteriaceae | |
| 147 | Crassulaceae | |
| 21 | Crotalidae | |
| 69 | Cruciferae/ Brassicaceae | |
| 376 | Ctenidae | |
| 101 | Cucurbitaceae | |
| 149 | Culicidae | |
| 151 | Cupressaceae | |
| 152 | Cuprum | |
| 238 | Cycadaceae | |
| 5 | Cyclic Carbon Compounds | |