102 



REPRESENTATIVE PLANTS 



Type 6. Zygnema ' 



Habitat and appearance. The plant grows in localities 

 similar in nature to those where spirogyra is found. It 

 may often be distinguished by its yellow hue. It is easily 

 grown in the laboratory. 



Structure. Examine a very small portion of the alga 

 (remember that all the green water plants, or scums, and 

 the pleurococcus, besides many otlier forms, all containing 

 chlorophyll and living in water, and lowest in the plant 

 scale, bear this name) and treat it as you did spirogyra, (m), 

 (Ij)), (Jip), unstained and iodine-stained. Observe that the 

 cells are shorter relatively than those in spirogyra, and 

 especially observe the very different form of the two clilo- 

 roplasts found in each cell. Examine very carefully and 

 see if you cannot compare the chloroplast to an irregular, 

 many-pointed star. 



By very close observation find an almost transparent 

 connection between the chloroplasts, containing within it the 

 nucleus. This feature is seen more easily in the iodine- 

 stained preparation. 



Reproduction. This alga reproduces as spirogyra does. 

 Seek for either form of reproduction found in that plant. 

 Make careful drawings covering the important features 

 you have discovered. 



Comparison, ('ompare spirogyra and zygnema by means 

 of this table : — 



Name 



Spirogyra 

 Zygnema 



Color 



Feemng 



Cell Ratio. 

 Length of 

 Diameter 



Size 



CULORO- 

 PLA8T8 



1 A plant allied to spirogyra. 



