Netrium digitus (mouse-over picture showing two different planes of focussing)
cell dimensions (L x B): ca 250 x 50 µm
Netrium digitus is one of the most common desmid species in acidic habitats. Actually, it is not a ‘real’ desmid, i.e., it does not belong to the family of Desmidiaceae (placoderm desmids) but to the more primitive family of Mesotaeniaceae (saccoderm desmids) characterized by a cell wall that consists of but one single piece. The large, more or less cigar-shaped cells of Netrium digitus are always readily to be distinguished by their characteristic chloroplast structure. For the longitudinal chloroplast ridges are regularly scalloped and the lobes thus formed are alternately bent in two different directions.
image @ Wim van Egmond
Detail of chloroplast structure in Netrium digitus
Focus-through video of the cell of Netrium digitus in apical view showing radiating chloroplast lobes, towards the periphery splitting into smaller lobules.