tSO PHYSIOLOGY. 



vegetable mucilage, cytohlastema, &c. The cell-wall or membrane 

 of cellulose takes no part in the formation of cells.* 



Cells originate in one of two ways : either free in the cavities 

 of older cells, or at least in the protoplasmic fluid elaborated by 

 their agency ; or by the division of such cells. The first is called 

 Free Cell-formation or original cell-formation, being the first 

 phenomenon in the life of every plant ; the second, Cell-division 

 or Cell-multiplication, which is the usual mode of growth in the 

 nutritive organs of vegetables. 



A, Free Cell-formation.— We may distinguish two modifi- 

 cations oi free cell-formation. 1. Free cell-formation from a 

 nucleus or cytoblast ; and, 2. Without the previous formation of 

 a nucleus. 



a. Free Cell-formation from a nucleus. — This mode was disco- 

 vered by Schleiden, who considered it to be the only process of 



■'^ Professor Lionel Beale has much simplified the nomenclature 

 of histology. He discards the term " cell," preferring the expres- 

 sion elementarypart, as less liable to mislead. According to this 

 able microscopist, every " elementary part " consists of two kinds 

 of matter, or of matter in two states : the one he terms germinal 

 matter, which is vitally active; the o^ih&T, formed material, which 

 is physiologically dead. The protoplasm, primordial utricle, and 

 nucleus of vegetable cells are of the first kind, and the cell- wall 

 — which Dr. Beale has shown to be not a necessary part of the 

 cell — the starch granules, &c. are examples of formed material. 

 This latter may have very various appearances, whilst germinal 

 matter is always the same. 



These two conditions of organised matter may be readily 

 distinguished under the microscope by the use of an alkaline 

 solution of colouring matter, e. g. carmine ; this is taken up by 

 germinal matter, which becomes deeply coloured, whilst formed 

 material is unaffected. In vegetable tissues the formed material 

 is generally thin, but in some animal tissues, as tendon, it is of 

 great thickness ; it must in every case have been at one time 

 germinal matter, from which alone can formed material be pro- 

 duced. Nutrition is effected by the constant passage of nutrient 

 matters from without inwards through the formed material to 

 the germinal matter, whilst the direction of growth is from within 

 outwards, the new formed material being interior to that of 

 longer existence. 



Dr. Beale regards the nucleus as a new centre of nutrition 

 and growth formed from the pabulum within one already exist- 

 ing ; cell-formation, as he describes it, is more nearly what is 

 usually called gemmation or budding, all germinal matter being 

 capable of division and increase, and of producing germs similar 

 to that from which it descended- 



