Contributions to Oar Knowledge of the FreslLivater Ahjae of Africa. 4^7 
cells, and, as a consequence, it lias been difficult to obtain conclusive 
evidence on this point. Even tlie thread shown in Fig. 20, I, is not 
beyond suspicion, as the second cell from the left was empty, although 
Fig. 20. — Spirogijra decimina (Mnell.), Kuetz., var. injiata, F. E. Fritsch, 
nov. var. A, male thread, showing the empty conjugating cells and the 
inflated non-conjugatino^ ones. B, two vegetative cells (the contents are 
shoAvn contracted, as they appeared in the material). C, small part of a 
female thread showing an almost globular zygospore and a non-inflated 
vegetative cell. D, small part of a male thread, on a larger scale than in 
A. E-H, different forms of zygospoi^es. I, female threads showing zygospores, 
a possible male cell, and inflated vegetative cells. A and J x 90 ; the 
remaining figures x 225. 
provided with a conjugation canal, indicating the possibility that here 
conjugation with a third thread had taken place, the cell in question having 
behaved as a male. 
"The cells containing the zygospores never showed any trace of inflation, 
although generally rather short as compared with the ordinary vegetative 
