24 PLANT-LIFE 



saprophytes or parasites, obtain their food- supply from 

 organic matter made possible by green plants; and also 

 parasitic flowering plants such as the Broomrape and 

 Tooth wort, which absorb their nutriment from the tissues 

 of their living hosts. 



Furnished with some knowledge respecting the use of 

 chlorophyll, we are prepared to advance another step in 

 our study of the humbler forms of plant-life. The 

 Bacteria, to which we have devoted some attention, are 

 often classed as SCHIZOPHYTA (Gr. schizein, to cleave; 

 phyton, plant), or Fission- Plants, from their manner of 

 multiplication, and the Blue-Green Algse (Cyanophyceae) 

 come under the same category. These minute blue- 

 green plants, of which about 800 species have been 

 distinguished, are all too small for naked-eye observa- 

 tion. They contain chlorophyll and an additional blue 

 pigment, phycocyanin, which, unlike chlorophyll, is 

 soluble in water; this pigment gives the cells a bluish, 

 reddish, or violet cast. They occur in stagnant water, 

 on damp earth, in the sea, embedded in the tissues of 

 other plants, and some of them are associated with 

 certain Fungus plants which form Lichens. The struc- 

 ture of the cell is simple. In its centre is a colourless 

 body which is thought by some to be a nucleus, but it is 

 questionable if a duly constituted nucleus exists. The 

 cell- wall is gelatinous, and it is owing to the swelling of 

 this gelatinous membrane and its adhesive nature that 

 the cells, or filaments of cells, cling together and form 

 colonies. Chitin may also occur in the cell- wall. The 

 Blue-Green Algae thrive in great extremes of temperature : 

 they are found thriving in thermal springs at a tempera- 

 ture up to 85 C., and can exist in glacier streams. After 



