PLANT LIFE 151 



Rhizosolenia, before it has developed its 

 silicated cell-wall. 



Green Algce (Chlorophycese) are poorly 

 represented in the ocean, and in the phyto- 

 plankton practically only by the genus Halo- 

 sphcera, a small spherical alga of bright green 

 colour, known to Italian fishermen as " punti 

 verdi " (green spots). Indeed the green colour 

 so characteristic of most terrestrial plants is 

 found in only a few marine plants. Halo- 

 sphcera occurs nearly everywhere in the surface 

 and subsurface waters, except in the Arctic 

 and Antarctic, but never in great abundance. 

 Unlike most algae, it is reproduced by zoo- 

 spores. It has been taken in closing nets near 

 the lowest limit of the penetration of sunlight 

 in the open ocean, but in this position was 

 probably dead and falling to the bottom. 



Bacteria. — These plants are often regarded 

 as the lowest forms of life. This does not 

 mean that they were the first living organisms 

 on the earthy where life probably appeared 

 long before bacteria. They have doubtless 

 undergone evolution, and had not always 

 their present appearance. They are related 

 to the Fungi, and are the most numerous and 

 most widely distributed of living things, 

 being present everywhere in earth, air and 

 water, and occurring as parasites in plants and 

 animals. Under the microscope they appear 



