THE PHASE OF ELONGATION. 



4%l 



in long flower-stalks 10-20, or even 50-80 centimetres. It often happens, however, 

 that the growth in length generally, by elongationj is very insignificant, particularly 

 in shoot-axes ; so that the fully developed leaf-bases completely cover the shoot-axes, 

 as in the Fern Aspidium filix-mas, and in all cases where so-called radical rosettes 



Fig. 257. — Growing-point of a root of Maize {Zea Mays), a a older portion of root-cap ; i younger 



part of same ; J _apex of growing-point ; e e external layer of tissue of root — the cell-walls are 



tliiclcened (7; z*) ; r »- young cortex ; ff cells of axial vascular bundle ; g flattened cells of a large 



vessel, which will subsequently form long cylindrical segments with bordered pits ; m parenchyma 



. of the pith in the axial strand (highly magnified). 



are formed by the leaves. If the points of insertion of the leaves are pushed apart, 

 the shoot-axis forms intemodes or interfoliar parts between them. 



By the mode of growth of shoot-axes during the phase of elongation, therefore, 

 a very material influence is exerted on the definitive form of the entire shoot ; in so 

 far that it depends upon this, for example, whether the leaves are situated close 

 above one another and form a rosette, or are removed some distance apart, and 

 arranged in whorls, or are situated alternately or scattered on the elongated stem. 



