C 46 3 



CHAPTER VII. 



OF THE MEDULLA OR I'lTH 



The centre or heart of \he vegetable body, within the 

 wood, contains the Medulla or Pith. This, in parts 

 most endued with life, as roots, and young growing 

 stems or branches, is a tolerably firm juicy substance, 

 of an uniform texture, and commonly a pale green or 

 yellowish colour. Such is its appearance in the young 

 shoots of Elder in the spring ; but in the very same 

 branches, fully grown, the pith becomes dry, snow- 

 white, highly cellular, and extremely light, capable of 

 being compressed to almost nothing. So it appears 

 likewise in the common Red or White Currant, and 

 numerous other plants. In many annual stems the pith, 

 abundant and very juicy while they are growing, be- 

 comes little more than a web, lining the hollow of the 

 complete stem, as in some Thistles. Many grasses and 

 umbelliferous plants, as Conhim maculatum or Hemlock, 

 have always hollow stems, lined only with a thin smooth 

 coating of pith, exquisitely delicate and brilliant in its 

 appearance. 



Concerning the nature and functions of this part va- 

 rious opinions have been held. 



Du Hamel considered it as merely cellular substance, 

 connected with what is diffused through the whole 

 plant, combining its various parts, but not performing 

 any remarkable office in the vegetable ceconomy. 



Linnaeus, on the contrary, thought it the seat of life 

 and source of vegetation ; that its vigour wa;s the main 



