2094 Journal of Applied Microscopy 



grassy banks of ponds in city parks. The body of the alga is made up of a very 

 great colony of cylindrical coenocytes arranged in the form of a sack-like net. 



1. Examine a large plant and describe the naked-eye characters. 



2. Draw a small portion of a young net under low power, showing how the 

 meshes are formed by the joining of a number of coenocytes. Describe. 



3. Under high power draw a single coenocyte, showing the chloroplast and 

 numerous pyrenoids. 



4. Vegetative propagation. Study and draw a large coenocyte of an old 

 net in which the cells ^are developing a daughter net. 



XXI. Cladophora Sp. Family, Cladophoraceae. 



Species of Cladophora are commonly found in flowing water. They appear 

 as large, dark green, extensively branched tufts attached to rocks and pieces of 

 wood. These algae are also abundant along the shores of lakes, where they may 

 often be found attached to objects which are exposed to the action of waves. 



1. Describe the naked eye characters; size, mode of growth, color, habitat, 

 etc. Note the differentiation of base and apex. 



2. Mount a small branch of the thallus in water and study under low power, 



3. Under high power study the stages showing the development of a branch. 

 Make four drawings showing four general stages : (1) a small bulging out of 

 the cell wall on one side below a septum ; (2) a short branch with the proto- 

 plasm still connected with the parent coenocyte ; (3) the branch cut off from the 

 parent coenocyte by a septum ; (4) a branch divided by a transverse septum 

 into two coenocytes. 



4. Draw a single coenocyte or division between two cross walls, showing 

 the irregular chloroplasts and the pyrenoids. Notice the large central vacuole. 

 Apply salt solution and note the effect. Numerous nuclei are present, but these 

 can probably not be distinguished from the pyrenoids without special staining. 

 Draw. It is a coenocytic plant with numerous transverse walls, but the walls do 

 not represent cell divisions. How and where do the branches always originate ? 



5. Draw and describe an empty Cijenocyte or zoosporangium from which 

 zoospores have escaped. Where is the opening (ostiole) always formed ? 



6. At certain times zoospores may be seen forming and escaping into the 

 water. This frequently occurs in material which has been kept in water in a 

 warm room. Draw a coenocyte in which zoospores are developing. 



7. Draw a coenocyte in which the zoospores are fully formed. Look for 

 zoospores in the act of escaping through the ostiole. 



8. Study and draw free-swimming zoospores, showing the chloroplast and red 

 eyespot. To make the two flagella visible treat with iodin solution by placing 

 a drop on the slide beside the cover glass and letting it mix slowly with the 

 water of the mount. 



9. Draw a zoospore which has begun to develop into a new filament. 



10. The zoospores (planogametes) of some species are said to conjugate. 

 Look for such a process. 



Ohio State University. JOHN H, ScHAFFNER. 



