EXERCISE 94 

 EDOGONIUM 



Materials. This alga may be found attached to sticks and stones 

 in ponds and streams. Fruiting material should be preserved 

 when found. 



Directions for work. Compare the cells with those of Spirogyra. 

 Examine the attached end of the filament for the peculiar hold- 

 fast. This is particularly well seen on young filaments. 



If the material is fruiting, some of the filaments will contain 

 thick-walled sexual spores similar to those seen in Spirogyra. 

 Do all cells of the filament form sexual spores ? Other fila- 

 ments may show these in earlier stages, before the thick wall 

 has formed, illustrating all the stages in the transformation of 

 an ordinary vegetative cell into a sex cell (egg). 



Certain cells of the same filament or of other filaments 

 may be found wjiich have divided transversely, forming several 

 smaller cells. In each of these are formed two small sex cells 

 (sperms). These escape into the water and may swim to the 

 large sex cells and unite with them, one small cell uniting with 

 one large one. Afterward the thick wall forms. 



Can you distinguish the sexes here ? Is there any consider- 

 able amount of food material stored in either sperm or egg or 

 in the spore ? What is the advantage ? 



Reference 



BERGEN and CALDWELL. Practical Botany, p. 202. 



[iir 



