SECT. i. FORMATION OF CELLULAR TISSUE. 



171 



mordial cell, being sometiines attached to the internal 

 cell wall. 2 On the minute but complicated organ, the 

 primordial cell, vegetable life depends. 



It will be shown afterwards that the primordial cell 

 sometimes constitutes 

 the whole plant, with 

 or without its cellular 

 coat. By its continual 

 bisection when so 

 coated, linear plants, 

 such as the con- 

 fervse, are formed and 

 lengthened (fig. 3). 

 When bisection is 

 about to take place, 

 the cell increases in 

 length; the nucleus, 

 which always plays 

 an important part in 

 cell formation, spon- 

 taneously divides into 

 halves ; at the same 

 time the cell wall 

 becomes constricted 

 in the middle and 

 gradually folds be- 

 tween them, and di- 

 vides the original cell Flg ' 

 into two new ones, in 

 which the nuclei become perfect and assume their 

 normal position. The terminal cell may undergo the 

 same process, so that the plant may be lengthened 

 indefinitely. 



Plants which spread in two directions are formed and 



Development of Ulva : A, isolated cells; 

 c, clustered subdivided cells ; p, E, confervoid 

 filaments ; P, G, frond-like expansions. 



2 On the Functions of the Nitrogenous Matter of Plants.' By M. L. 

 G-arreau, ' Annales des Sciences naturelles/ t. xiii. 1860. 



