CHAPTER II. 



THE CELLULAR CONSTRUCTION OF THE PLANT. 



THE apical points of Stem and Root, described in the previous chapter, 

 cannot fail to have attracted attention, by reason of their continued 

 powers of growth and of forming new parts. The perpetual youth 

 of the extreme tips is their leading character. Passing back from 

 these we see parts in successive stages of development up to full 

 maturity. This shows from external observation that new parts 

 originate there. To understand how this takes place, a study of the 

 internal structure will also be necessary. Such study is called Anatomy, 

 for in large and solid bodies such as these it is by cutting into them 

 that their construction can best be made out. Two courses are open 

 for such study. A start may be made from the mature parts, such as 

 the fully formed stem, leaf, or root, in which the structure is very 

 complicated. Or the young embryonic tip itself may be examined first. 

 Since the construction is much simpler at the tip where the tissues 

 are still young, it will be found best to take this first. Moreover, 

 upon the result of this examination it is possible to base a genera) 

 idea of the construction of the whole Plant-Body and of all its mature 

 parts. 



If an apical bud of a water-plant, such as Hippuris or Elodea, be 

 dissected under a magnifying power of ten to fifteen diameters, a 

 succession of overlapping leaves will be found, those lying within 

 being constantly smaller than those outside them. The series may 

 be followed till the last are too minute for recognition with the simple 

 lens. In the centre is a projecting cone of soft colourless tissue, with 

 a dome-like ending. This is the apex of the stem, or growing point 



(Fig- 7). 



If a median longitudinal section be cut through a bud of Hippuris 

 ^so as to traverse this cone to its extreme tip, it would on microscopic 



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