WATEE SILK 53 



hours, and again the next morning before the sun- 

 light reaches the aquarium, and by individual fil- 

 aments. Put several filaments into a saucer of 

 water and note their shape, color, length, and 

 diameter. What variations do you find in these 

 features? If necessary use a magnifying-glass. 

 Does the plant grow attached to a substratum ? 

 Can you see any branches ? Boots ? Why is the 

 plant an inhabitant of stagnant water ? Feel of 

 the plants. What significance in the common 

 names ? 



II. Microscopical cha/raoters. 



Mount two or three filaments in water and ex- 

 amine first with a low, then with a high power, 

 and note : 



a. The shape of the JUament. — What is it ? Is its diam- 

 eter uniform ? What is the shape of the ends ? 

 Can you detect any branches or roots ? Has it a 

 " root end " and a " stem end " ? 



h. The si/ructxire of the individual filament. — Note that 

 the filament is composed of cells. How are the 

 cells arranged? What is the shape of a single 

 cell? What relation between its length and 

 breadth? Are all of the cells of this shape? 

 How are the cells connected ? Is there any dif- 

 ference between the two ends of the filament? 

 Be careful not to be deceived by injured cells, 

 which are frequently to be found at the end of 

 the filament. Look for a transparent, slimy coat- 

 ing covering the filament. This is seen best just 

 before a drop of stain reaches the filament. How 



