Desmidium swartzii is the most common filamentous desmid and is not only found in bogs. In my sampling site Simmelried it is very common and can usually be found between floating plant masses.

The filaments of Desmidium swartzii are not branched and can be easily recognized even at low magnifications, because the trigonal cells are connected slightly offset to each other and thus the filament appears twisted (s. fig. 1 a-c). The cells themselves consist of two half-cells, which are, however, strongly widened and flattened. Like the cells of the genus Staurastrum, they have an isthmus in the middle (s. fig. 2 a-b). Each half-cell has a chloroplast with three pyrenoids. At the outer angles of the cells there are contact surfaces with which the cells are connected to the neighboring cells (s. fig. 3). When the coverslip pressure is increased, these connections break and the trigonal shape of the cells can be seen in apical view (s. fig. 4).