54 MICROSCOPY FOR BEGINNERS. 



scientific names. These utricles are almost always con- 

 spicuous when the plant is taken from the water, as 

 small, green, semi-transparent particles attached to the 

 leaves. They are not unlike small pieces of jelly in 

 appearance, until examined with the microscope, when 

 their remarkable structure is seen. Until within a few 

 years they were supposed to act as air-sacs to help the 

 plant float. It was even said that they became filled 

 with air or gas at flowering-time, and so lifted the flow- 

 er-stalk and the bloom above the water. This was in- 

 teresting, but the truth is more interesting and star- 

 tling. The plant actually feeds on animals. These 

 bladder-like bodies are the food-traps, the mouths and 

 the stomachs of the Utricularia. 



Under the microscope they are seen to be hollow, oval 

 bodies, with a narrow, almost straight anterior end, and 

 several long bristles projecting forward or away from 

 the utricle, these bristles probably serving as a guide to an 

 opening at their base. The little animal swims or crawls 

 against a bristle, and naturally moves down it towards 

 the opening in the utricle, which it finds closed by a 

 transparent colorless curtain ; this it pushes aside and 

 passes on into the trap. The curtain-like valve is at- 

 tached by its upper and lateral margins, therefore hang- 

 ing before the opening in the utricle, and swinging in- 

 ward, but so arranged that it cannot be forced outward by 

 any creature small enough to pass within. Indeed, the 

 power that the valve seems to exert is somewhat astonish- 

 ing. Small fish have been found with the tail or even the 



