526 Annals of the South African Museum. 



transverse elongatis. Antberidia noil satis eognita, monoica vel dioiea. 

 Oosporae sphaericae vel ovales, lnembrana incrassata alata, bi- vel raro 

 tri- vel quadri-angulares. Post fecundationein membrana tenuis arcta 

 oosporam iuduit ; intra earn membrana niatura oosporae evolvit, postea 

 membrana prior rumpit et in vicinitate manet. 



Lat. cell. veg. in media parte, 42-78 /x: lat. cell. veg. in sept is 

 19-54 fi; lat. oogon., 39-60 /x; lat. oospb., 10-21 /x (pleruinque 

 18-21 fi) ■ lat. oosp. a latere, 20 x 12, 27 x 15, 27 x 18, 33 x 21 fi ; 

 lat. oosp. a superficie cum ala, 21, 24, 24 x 22, 25, 25 x 21, 28 x 24, 

 33 ji.. 



Samples 17, 18. 



Apart from Hydrodictyon africanum, this is probably the most 

 interesting form that the freshwater algal flora of South Africa has 

 yet yielded. 



The unbranched filaments are of very considerable length and con- 

 sist of " cells," which are in general much elongated (12-18 times as 

 long as broad), although very short ones are occasionally met with. 

 In the majority of cases the " cells " are much narrower at the septa 

 than in the middle, so that their shape is more or less that of an 

 elongated barrel (Fig. 15, C) ; these customary dimensions are illus- 

 trated by the table on p. 528. Filaments are, however, also found in 

 which this constriction at the septa is scarcely marked, and even the 

 reverse is occasionally encountered, the threads being widest at the 

 septa (e. g. in two cases noted the width of the threads at the septa 

 was 40 and 45 ^ respectively, the width of the appropriate "cells,' - 

 at their middle, 20 and 30 /x respectively). 



The chlorophyll-apparatus is composed of numerous small irregular 

 grains, only a small percentage of which contain pyrenoids ; the latter 

 are rather large and spherical (Fig. 15, A and B). The chloroplasts 

 and pyrenoids stained readily with methyl blue. In general the 

 arrangement of the chlorophyll-apparatus is very irregular (Fig. 15, A), 

 although a disposition in transverse rings, such as is customary in 

 8. annnUna (Roth), Ag., is not uncommon (Fig. 15, B). In a few 

 cases the chloroplasts were arranged in a spiral manner over short 

 stretches. The more or less irregular strands of protoplasm containing 

 the chloroplasts are separated from one another by large clear vacuoles 

 (Fig. 15, A and B). The rather irregular distribution of the chloro- 

 plasts, involving occasional massing at certain points, whilst some of 

 the small protoplasmic strands are quite devoid of them, hints at the 

 possibility of streaming of the protoplasm. Momentary staining with 

 Ehrlich's haematoxylin and subsequent treatment with Orange G shows 

 numerous small nuclei of a deep purple colour, in contrast to the pale 



