green & red filaments

描述：

Zygogonium (sigh-go-go-knee-um) a green filamentous alga, in which cells exposed to intense sunlight accumulate a soluble purple pigment formed from an iron-tannin complex within their cells. Some filaments here look green, others look purple. Phase contrast. Material from Nymph Creek and Nymph Lake, thermal sites in Yellowstone National Park, photograph by Kathy Sheehan and David Patterson.