86 



PRACTICAL BOTANY. 



high power on motile forms that have come to rest. It is 

 much easier to see them in stained preparations. Run a 



minute drop of iodine 

 solution under the cover 

 glass and watch its ap- 

 proach to the moving 

 organisms. As the or- 

 ganism dies the flagella 

 come into distinct view. 

 The flagella are believed 

 to be projections of the 

 protoplasm, and their 



FIG. 43. - Protococcus. a, an encysted cell mo vements are produced 



preparing to set free its four megazoo- 

 spores; b, a megazoospore or large mo- 

 tile form. 



by the alternate con- 

 strictions of the proto- 

 plasm on their opposite sides. Draw a cell showing fla- 

 gella. The rapid movements of the motile forms, and the 

 fact that some species have contractile vacuoles, a char- 

 acteristic of the lowest forms of animals, have led to 

 doubts as to the classification of Protococcus. Some emi- 

 nent scientists class it as a plant ; others as an ' animal. 

 As already noted, the 

 possession of flagella in- 

 dicates close relation- 

 ship with the Volvoci- 

 nese. It is known that 

 after a time the motile 

 forms come to rest, draw 

 in their flagella, and be- 

 come invested with a 

 thick cell wall. They 



are now resting spores. F IG- 44. Protococcus. An encysted cell 



preparing to set free microzoospores. 



6. Pmd large en- 

 cysted cells of Protococcus in which the cell contents are 

 broken up into separate parts. The megazoospores are pro- 



