44 
Transactions of the Royal Society of South Africa. 
Aspectus verticalis et lateralis typo similes sunt. Long, cell., 75-88 ju ; lat. 
cell., 48-58 /i; lat. istlmi., 16-1 8 /i; crass. 35-36/1. 
Sample 327 (very rare). 
This variety is characterised by the complete rounding off of the apices 
of the semicells and by the more irregular arrangement of the granules, 
especially in the centre of the semicell. It appears to bear the same rela- 
tion to the type as var. siibrotundatum, West, does to C. consjjersum, Kalfs. 
Schmidle (Alg. Carolinen, Hedwigia, xl, 1901, p. 347, Tab. XII, tig. 6) 
has described a var. major of C. margaritatum (Lund.), Eoy et Biss., which 
comes rather close to this variety of C. gayanum. 
Forma paullo minor, isthmo valde incrassato, granulis saepe plus minus 
excavatis. Long, cell., 48-57 ; lat. cell., 44-52 ju; lat. istlim., 15-1 8 
(Fig. 19). 
Samples 327, 331, and 336. 
This form, as far as dimensions are concerned, comes between var. minus, 
Nordst., and the type, but it is especially distinguished by the strong 
thickening of the membrane at the inner edge of the isthmus, which is usually 
more or less triangular in shape ; the thickening and longitudinal extension 
of this region was sometimes even more pronounced than in Fig. 19. An 
isthmus of a similar character is found in C. orthopleurum, Roy et Biss. 
ourn. Bot., xv, 1886, p. 194, Tab. 269, fig. 16), which is probably but 
a variety of C. quadrum, in which, however, intergranular punctations are 
present. The granules in the present form wei'e generally more or less hollow 
