Spencer.—On the Fresh-water Algw of New Zealand. 297 
Pediastrum tetras, and P. heptactis are both common. 
” pertusum. Intestines of the frond hyaline; some of the inner 
cells are gone, therefore the foraminal appearance is uncertain. The 
rectangularity of the outer row of cells and the shape of the notch point to 
pertusum. On the other hand, the number of rows, and the number of 
circumferential cells, might lead one to infer a new species. On careful 
comparison, however, I am inclined to consider it as an unusually large 
specimen of P. pertusum. Number of rows, five; number of cells in inner 
circle, five. The two next rows are broken down. The fourth circle con- 
= apparently eighteen, and the outer one—the fifth—twenty-one cells. 
Pediastrum, spn. Frond square, divided into four equal lobes by a 
crucial hyaline division. Lobes divided into segments by a deep narrow 
notch, which extends from the four corners towards the centre of the frond, 
the segments again partially subdivided by a broad shallow notch. Side 
view, four cells placed end to end, the central ones about twice the size of 
the terminal. Although at first sight so very unlike, there is a remarkable 
similarity between this plant and P. tetras ; in fact, the only point of differ- 
ence consists in the secondary segmentation of the lobes. Hig, 10. 
Scenedesmus quadricauda. I have placed before you a figure of this 
Desmid, because it shows the unusual phenomenon of a broad well-defined 
coating of hyaline matter external to the cells, and further that the bristles 
appendages of the investing coat and not of the cells themselves. 
ig. 11. 
DiaTomacez. 
Meridion constrictum, H., xevi.; M.Dic., 12. 
Diatoma elongatum, H., xciv. 
» vulgare, H., xciv.; M.Dic., 12. 
mpylodiscus costatus, M.Dic., 12. 
abc bifrons,-M. Dic., 18. 
Synedra splendens, H., xevii. 
Navicula, 
Gyrosigma macrum, M.Die., 11. 
: Be aitenuatum, M.Dic., ii 
Pinnularia oblonga, M.Dic., 11. 
