60 DROPS OF WATER. 



The first section, the Desmidiea, are a family 

 of microscopic Algae, distinguished, like most 

 other plants, by their green colour ; they are 

 formed of vessels or cells containing a green sub- 

 stance. These cells, or joints, separate either com- 

 pletely or only partially, some genera forming 

 long filaments, by the union of many cells, and 

 others are seen generally only in pairs. I shall 

 describe a few of the most singular in appear- 

 ance, and those most commonly found. 



The genus Desmidium is seen as a long, pale 

 green filament, formed of many cells. There 

 are two species. Desmidium Swart zii (Plate I. 

 fig. 1) has three edges, forming a triangle 

 when viewed transversely ; when many cells are 

 connected together, and the filament is lying 



