Tribonema (tribe-owe-knee-ma) is a xanthophyte, a group of stramenopiles with chloroplasts. Xanthophytes may adopt a variety of body forms, and the normal form for this genus is the filament. Cell walls often built from H-shaped units, and these overlap in the middle of a cell. Stalked attached cells also occur, as is evident here. Plastids usually discoid, yellow green. Differential interference contrast.