AQUATIC PLANTS USEFUL TO THE MICROSCOPIST. 53 



often been mistaken for it. To make such an error is 

 of no great consequence, unless it should lead the ob- 

 server to imagine, as it once did the writer, that he has 

 found a rare species of Myriophyllum. Yet it is always 

 pleasant, if nothing else, to feel sure, and it is more than 

 pleasant to have a reputation for accurate observation. 

 Proserpinaca, however, is as useful a trap as Myriophyl- 

 lum, and it can be easily distinguished because the dis- 

 sected leaves are not in an exact circle around the stem : 

 one is on one side, the next a little further round and a 

 little higher on the stem, another still further round and 

 nearer the first, but still higher. They are what the bot- 

 anist calls alternate. 



Either of these plants is a specially good place for 

 attached diatoms (Chapter III.). 



UTRICULARIA (Figs. 9 and 10). 



Of all our water-plants with finely divided 

 Utricularia is probably the most interesting in 

 and one that can always be recog- 

 nized at a glance. It is found in 

 long, somewhat branching streamers, 

 floating freely below the surface or 

 very slightly rooted. A leaf of Utri- 

 cularia vulgdris, a common species, 

 is shown somewhat enlarged in Fig. 

 9, with the peculiar hollow bladders, 

 or " utricles," that distinguish it from 

 all other plants, and give it one of its 



leaves, 

 itself, 



Fig. 9 A Leaf of Utricn- 



laria. 



