Freshwater algae of Southern Africa. II. Triplastrum spinulosum from the Transvaal

The presence of Triplastrum spinulosum (Kisselev) Gauthier-Lievre (Desmidiaceae) in South Africa is reported for the first time. The characters of T. spinulosum varieties spinulosum, indicum (Iyengar & Ramanathan) Gauthier-Lievre and  africanum Gauthier-Lievre were found to be exhibited by specimens collected at Ottosdal in the south-western Transvaal. The differences among specimens of the populations studied are ascribed to variation within one variable species and therefore the varieties  indicum and  africanum are relegated to synonymy.


M ETHODS
The material was preserved with 4°0 formalin. Slides were made by mounting a sample droplet in a drop of glycerine. The methods used for the drawings and photomicrographs were the same as those given in the first paper of this series (Claassen, 1973). Iyengar and Ramanathan (1942) found a desmid in material collected during December 1940 in a paddy field near Madras, South India, which resembled the species Triploceras abbreviatum Turner (Krieger, 1937;Turner, 1892) and Triploceras simplex Allorge (Krieger, 1937). One of the main characters of the genus Triploceras Bailey is the presence of numerous whorls of knotlike projections (verrucae). As this character was lacking in both Turner's and Allorge's species as well as in their own taxon, Iyengar and Ramanathan (1942) decided to establish the new genus Triplastrum to accommodate these taxa, the consti tuent species being Triplastrum indicum Iyengar  1937), the description of which was based on a single specimen collected in Turkestan in 1930. Triploceras spinulosum closely resembles Triplastrum indicum and in 1960 Gauthier-Lievre reduced the latter to a variety of the former, thus Triplastrum spinulosum (Kisselev) Gauthier-Lievre var. indicum (Iyengar & Ramanathan) Gauthier-Lievre.
According to Gauthier-Lievre (1960), Triplastrum spinulosum var. indicum differs from the typical variety in its larger dimensions and longer more divergent polar lobes. Iyengar and Ramanathan's figures for this variety agree with Figs 2 (lower semicell) and 17 (cell on left) of the present paper as well as with some of the cells with four-lobed apices . The dimensions of these cells overlap both those of the type and var. indicum.
The two varieties are thus placed into synonymy and the circumscription of the species is amplified.
The geographical distribution of this species is:

-Turkestan (in a rice-swamp near W eliko-Alexewskoje). India (in a paddy field near Madras, December) A frica.-Sudan (in a swamp of the River Niger near Gao, December). French Equatorial Africa (Ubangi-Shari, February). Uganda (in a swamp on the road from Masaka to Kampala, August). Transvaal (in a small pool on the banks of the Nyl River near Naboom spruit, February; in a small pan near Ottos dal, February and April).
It seems that this species is very rare and that usually only a few specimens are found in samples collected. In the samples collected near Ottosdal during April 1972, however, it was fairly abundant.
As could be expected in a fairly large population anomalous specimens were also found. In the Ottosdal material one specimen was found where, in each semicell, one of the polar lobes was under-developed, without spines and somewhat subapical (Figs 12,41). In another specimen only one of the semicells was like this (Fig. 13, lower semicell). Several asym metrical cells were found (Figs 11, 29, 40) and one very narrow semicell was observed (Fig. 30). The most anomalous specimen was a single semicell with a prominent basal inflation encircled by a whorl of eight lobes similar to the polar lobes (Figs 15, 42-44). In the Mosdene material one anomalous specimen was found with the polar lobes of one semicell undeveloped (Fig. 14).