BOTANY OF THE LIVING PLANT 



D 



Fig. i. 

 Cells of Pleurococcus Naegelii. Chod. 



Highly magnified, the powder is seen to consist of single spherical 

 cells, or groups of cells (Fig. i). Each of these cells is an individual 

 Plant, and it multiplies by division. The results of such repeated 

 divisions may remain for a time coherent, thus forming groups of 

 varying number. But finally they separate, and each single cell can 

 continue its life as a distinct unicellular organism. It is called 



Pleurococcus Naegelii. It may be 

 held as taking a low place in the 

 scale of vegetation, and would be 

 classified near to the beginning of our 

 Series. 



On the other hand, ordinary herbs, 

 shrubs and trees are examples of more 

 elaborate organisation. Each one of 

 these is composed of various large and 

 complex parts, which are united to 

 form the complete Plant. The sev- 

 eral distinct functions which they 

 perform benefit the whole. Such 

 n=nucieu°s WS *£££^$S*$*± Plants may attain large size, and very 

 e shows packed SS&ng from divi- complicated structure, as in the case 

 sioa. (After chodat.) Q | f orest trees (Frontispiece). Each 



of these Plants is an independent individual. Their increase in number 

 is by Seeds, produced through the process of flowering. The pro- 

 duction of seed is an involved and elaborate process, as will be seen 

 when it is described in later Chapters. Partly on the ground of 

 their complex structure, and partly because of the elaborate method 

 of their propagation, such Flowering Plants, or Seed-Plants, are ranked 

 as higher in the scale. Between such extremes as Pleurococcus and a 

 Flowering Plant other intermediate types may be ranked according 

 to their structure and their method of increase. And so a Series 

 may be found leading from those which are comparatively simple, 

 by gradual steps, to those which are more elaborate. Such a Series 

 is believed to illustrate roughly, and with some degree of truth, the 

 course which the Evolution of the Vegetable Kingdom has actually 

 followed. The simpler examples are held to represent such types as 

 appeared earlier in the History of Descent, and thus to be more 

 primitive. The types which are more complex in structure, and in 

 their method of propagation, are believed to have appeared later in 

 the History of Descent, and are regarded as derivative. This agrees 

 essentially with the sequence of fossils embedded in successive 



