Gloeotrichia Agardh

 From Greek gloia, "glue" + thrix, "hair"
 
Note the rounded, basal heterocysts and the
elongated akinetes immediately adjacent to them.
 

The filaments sometimes arrange radially to form spherical or hemispherical colonies surrounded by distinct, firm mucilage. These colonies may be microscopic or as large as several centimeters.

Gloeotrichia filaments have distinctive basal heterocysts and akinetes and tapered apical hairs. The trichomes themselves may be tapered or constricted, and are straight, curved, or bent in form. Rarely, false branching occurs as branches grow parallel to the main filament. The cells may
be barrel-shaped, cylindrical, or elongated and hair-like, and blue-green, red, or brown in color. The cells sometimes contain groups of gas vesicles.
 
The heterocysts are spherical, ellipsoidal, or hemispherical and usually grow at the end of the filament. The akinetes are more elongated in form and have rounded ends, and sometimes form chains. Akinetes develop when vegetative cells adjacent to the heterocysts begin to enlarge and form thick walls. The akinetes can then separate from the sheath containing the rest of the filament and germinate to produce new growth.