CHAPTER II. 



PLANT STRUCTURE AND GROWTH. 



ALL plants commence existence as a single cell, like 

 Torula or Protococcus, and it is only by the multi- 

 plication of these cells, the alteration of their form 

 by pressure against each other, and their development 

 into tubes, &c., that we get the wonderfully varied 

 and beautiful forms of higher plant life. As we have 

 seen, the lowest forms of plants are unicellular, but 

 from these to the complex organisation of the forest 

 trees there is a very gradual advance. In the same 

 group as Protococcus the Algce we have plants with 

 a larger number of cells, as Zygncema and Oscillatoria. 

 In the division of Fungi we have a similar advance 

 from the simple form of Torula, through the moulds 

 with strings of cells placed end to end, up to the 

 mushrooms and toadstools. From the remarks in 

 the previous chapter, it will be seen that plants are 

 divided into two great groups, those that possess 

 chlorophyll green plants and those that do not 

 fungi. 



The green plants are again broken up into other 

 divisions, according to the complexity of their organ- 

 isation. 



In Zygncema we have seen how the normal form 



