58 MICROSCOPY FOR BEGINNERS. 



thinner fronds. It is lighter green in color, the lower 

 surface is never purplish, and it has but one rootlet to 

 each frond. Both species have a curious little 

 ^^ cap on the free end of each rootlet. It is more 

 easily seen with the naked eye on Lemna polyr- 

 rhiza, where it is usually darker than the rest 

 of the rootlet. 



There are several other species, but they are 

 so seldom found that they are not included in 



Xlg. 13. 



L6mna this list. They all multiply by the growth of 

 young fronds from the edges of the old and 

 mature. This accounts for the clusters so commonly 

 seen. They also bloom, but the flowers are extremely 

 small and are rarely observed. The student will be fort- 

 unate to find specimens in blossom. The flowers burst 

 out of the margin of the frond, and consist of only 

 those parts needed to fertilize and mature the few small 

 seeds. 



The rootlets are valuable to the microscopist, as they 

 are favorite places for many just such creatures as he 

 most wants. The lower surface of the fronds, especially 

 of Lemna polyrrhiza, should be gently scraped in a drop 

 of water for Rotifers not often found elsewhere. It is 

 also much visited by small worms, but not so frequently 

 as the leaves of the white water-lily. 



ANlCHARIS CANADENSIS (Fig. 14). 



This is readily recognized by the arrangement of the 

 leaves in circles, or whorls, of three each, two of which 



