264 G. T. HARRIS ON THE DESMID FLORA OF DARTMOOR. 



vertical view of supernumerary semi-cell ; B, front view 



of cell. X 510. 

 Fig. 7. Xanihidium Rohinsonianum Arch, forma, x 510. 

 ,, 8. Staurastrum O'Mearii Arch, forma, x 510. 

 ,, 9. Staurastrum retusum Turn. var. boreale W. and G. S. 



West. X 510. 

 ,, 10. Zygospore of Cosmarium Brebissonii Menegh. x 310. 

 ,, 11. Zygospore of Roy a ohtusa var. montana W. and G. S. 



West. X 510. 



