Cylindrospermum Kützing ex Bornet et Flahault
From Greek kylindros, "cylinder" + sperma, "seed"
Large, ornamented, ellipsoidal or spherical akinetes usually develop from the lowermost vegetative cell adjacent to the terminal heterocysts, but are not always present in culture. There may be a single akinete or as many as seven. Many species can be differentiated based on akinete shape.	Cylindrospermum has curved or slightly coiled cylindrical filaments composed of square or rectangular vegetative cells. The gray or blue-green colored cells lack gas vesicles but sometimes have visible granules. The trichomes are enclosed in loose, colorless, homogeneous mucilage.   Normally, basal heterocysts form from the terminal vegetative cells at one or both ends of the filament. Cultured specimens may have both intercalary and terminal heterocysts. The heterocysts are conical, oval, or ellipsoidal with a single pore.     Cultured specimens with rounded vegetative cells and both terminal and intercalary heterocysts look very much like Anabaena filaments.     Terminal heterocysts have a single polar nodule, while intercalary heterocysts have two (arrows, left image).