Pleurotaenium subcoronulatum var. maximum Van Oye 1953: 262

Levanets, Anatoliy & Vuuren, Sanet Janse Van, 2024, New insights into the morphology, taxonomy and geographical distribution of Pleurotaenium subcoronulatum (Zygnematophyceae, Desmidiales), Phytotaxa 655 (2), pp. 144-158 : 152

7. Pleurotaenium subcoronulatum var. maximum Van Oye 1953: 262 , fig. 31.

Type locality: Belgian Congo [now Democratic Republic of Congo], environs of Stanleyville [now Kisangani, Tshopo Province], pond II, 1 May 1926.

Description: Cells are characterized by extremely large dimensions compared to the type, as well as all infraspecific taxa. According to the initial description of P. subcoronulatum by Turner (1893) cells are 340–400 in length and 28–32 µm wide (other publications, listed in Table 2, mention slightly different dimensions for the type). According to Krieger (1937) P. subcoronulatum var. africanum has a length of 372–450 μm and a width of 24–38 μm, while P. subcoronulatum var. detum has a length of 385–690 μm and a width of 24–25 μm. West & West (1896) indicated dimensions of 404–446 µm (length) x 29–38 µm (width) for P. subcoronulatum var. detum . In comparison with the dimensions mentioned above, cells of P. subcoronulatum var. maximum are much larger, with a length of 900–973 μm and a width of 60 μm and the length to width ratio is 16–16.5 ( Van Oye 1953). The number of visible apical tubercles is 14–15 and the cell wall is punctated. According to Van Oye (1953) the variety cannot be confused with other taxa due to a lack of undulations between the apex and the well-pronounced basal swelling ( Fig. 4F ).

Distribution:

Africa: Democratic Republic of the Congo ( Van Oye 1953).

Figures

FIGURE 4. Comparison of the morphology of P. subcoronulatum with closely related infraspecific taxa. A) P. subcoronulatum (from Turner 1893), B) P. subcoronulatum (from West & West 1895, C) P. subcoronulatum f. elongatum (from Prescott et al. 1975), D) P. subcoronulatum var. africanum (from Krieger 1937), E) P. subcoronulatum var. detum (from West & West 1896), F) P. subcoronulatum var. maximum (from Van Oye 1953), G) P. subcoronulatum var. rectum (from Borge 1903) and H) P. subcoronulatum var. spinulosum (from Opute 2000). No scale bars; dimensions indicated in descriptions.