CHAPTER I. 

 ALG.E 



PROTOCOCCUS 1 



Habitat and Morphology. Protococcus is a unicellular 

 green plant found growing on tree trunks and various moist 

 objects. It often occurs in such quantities as to impart a 

 bright green color to the trunks of trees. 



Histology. It is so small that its structure is seen only 

 when examined under the microscope. In its normal con- 

 dition it is a spherical cell, appearing bright green, except 

 for an outer layer or cell wall, which consists of cellulose. A 

 nucleus is present, but it is not visible unless decolorized and 

 stained. Protococcus usually occurs in the non-motile state 

 but under certain conditions the cells become motile and 

 swim freely about by means of two cilia. 



Reproduction. The only known method of reproduction 

 is asexual, by simple fission or division. Frequently the 

 two daughter cells resulting from a division of a mother cell 

 do not separate at once but the daughter cells divide in 

 another plane while still unseparated. Frequently also, 

 divisions occur in a third plane, so as to build up a cubical 

 mass of cells which finally divides into separate plants. This 

 method of division indicates the way by which the higher 

 plants were formed from unicellular ancestors. 



1 Protococcus viridis Ug. = Pleurococcus NaegeUi chodat = Pleurococcus 

 vulgaris of modern writers, not of Meneghini. 



