io6 



CELLULAR CONSTRUCTION 



[CH. 



presently be shown. But before this point is taken up a just opinion as to 

 the real nature and behaviour of these cells must be formed. In the first 

 place, though in cell-lineage they are the ultimate parents of all the tissues, 

 they do not actively dominate the apex. The growth in them is actually 

 slower than at any other point in the near neighbourhood, a fact that is 

 closely related to their very existence. Moreover in the actual scheme of 

 construction initial cells possess negative rather than positive characters. 



C B 



Fig. loo. Apical views of growing stem-apices of dorsiventral Ferns. j-^= initial cell of stem: 

 ^/= young leaves: .S^initial of alateral shoot: / = ramenta. A = Pieridinfji aquilinutti (L.), two- 

 sided biconvex initial cell of stem, with one young leaf. B, C=Polypodiujn vulgare L. j5 = three- 

 sided conical initial cell of stem with two young leaves, and the ends of several young ramenta. 

 C=three-sided conical initial cell of stem with a lateral shoot {S), and a young leaf. ( x 280.) 

 (After Klein, from Engler and Prantl.) 



Sachs has shown how solid meristems conform to a scheme of construction 

 built up of two systems of confocal parabolas the one periclinal the other 

 anticlinal, together with walls also in radial planes. These all cut one another 

 at right angles. He compared the very complete system of partitioning walls 

 in Flowering Plants with those less complete systems in plants like the Pteri- 

 dophyta, where apical cells are present. From this comparison he concluded 

 that an apical cell "represents merely a break in the constructive system of 



