Ranunculus pedatifidus (surefoot buttercup)

Centaurea solstitialis (yellow star-thistle)
Centaurea stoebe ssp. micranthos (spotted knapweed)
Centaurea tenoreana
Centaurium calycosum (Arizona centaury)
Centaurium erythraea
Centaurium exaltatum (desert centaury)
Centaurium pulchellum (branched centaury)
Centaurium spicatum (spiked centaury)
Centaurium texense (Lady Bird's centaury)
Central African Republic
Centranthus ruber
Centrosema virginianum (spurred butterfly pea)
Cephalanthera damasonium
Cephalanthus occidentalis (common buttonbush)
Cerastium arvense
Cerastium arvense (field chickweed)
Cerastium arvense ssp. velutinum var. velutinum (field chick
Cerastium glomeratum
Cerastium holosteoides
Cerastium nutans var. nutans (nodding chickweed)
Cerastium semidecandrum (fivestamen chickweed)
Ceratostigma plumbaginoides
Cercocarpus montanus (alderleaf mountain mahogany)
Ceropegia linearis
Chad
Chaenomeles x superba
Chaenorhinum minus
Chaenorhinum minus (dwarf snapdragon)
Chaerophyllum bulbosum

Image of Ranunculus pedatifidus (surefoot buttercup) 1
USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Vol. 2: 108.