Plate Y 



20. Cosmarium margaritiferum. 



21. Cosmarium margaritiferum 

 (empty frond). 



22. Cosm. margaritiferum (end view). 



23. Anldstrodesnms falcatus. 



34. Figure of a Bottle attached to tho 

 end of a walking-stick by an 

 india-rubber band. 



2- r >. Navicula didyma. 



26. Pinnnlaria major. 



