50 THE VEGETABLE KINGDOM. 



power. The frustules, or valves, are quite apparent cylin- 

 drical, round at the edges, and with a strongly-marked 

 central line. Some of the frustules are larger than others ; 

 in these most likely the process of self-conjugation has 

 begun. 



ACHNANTHES LONGIPES, 

 From achne (chaff or down), and anthos (a flower). 



These now scattered frustules were connected in life by a 

 stem, and the upper and lower frustules had different 

 markings. You may observe that some have a transverse 

 line, forming a cross upon the valve; this is one of the 

 lower frustules. Achnanthes are common in sea-water, 

 attached to algse. There are several species, some fossil, 

 others found in fresh water ; but this is the most beautiful. 



SYNEDRA TJLNA, 



From sunedra (a sitting together), 



are common in fresh water, sitting together in groups of 

 golden wands, striated and open at the ends, which in age 

 dilate, and three obtuse teeth are visible, with openings 

 between them. These often occur in such numbers as 

 quite to encrust the confervse, or the stones in ponds and 

 rivers. 



We need but to take a very little of the brown-looking 

 vegetation which we find on the walls of wells or horse- 

 troughs, or quiet ponds, and, placing it on a slip of glass, 

 with a drop of water, cover with another piece of thin glass, 

 to see many of these living microscopic plants. 



BACILLARIJE. 

 From laculus (a staff). 



These are much shorter than Synedra, and are found 

 adhering together by one corner, in a zigzag manner, or 

 free, like naviculse, gliding about in a drop of water. They 

 are so abundant as to cover the confervse like felt. 



