168 



BOTANY 



obey the same laws as do weightless films of liquid. The cell wall tends at the 

 moment of its origin to assume the same position as a film ia a mass of soap-suds 

 would under similar conditions. 



True ROOTS are first found in the Pteridophytes, and in them 

 possess an apical cell in the shape of a three-sided pyramid ( 1;V -) (Fig. 

 167 /). In addition to the segments given off by the apical cell 

 parallel to its sides, it also gives rise to other segments (k) 



Ki<;. I'i7. Median longitudinal section of the apex of a root of 1'terix eretica. 

 t, Apical cell : 7>-, initial cell of root-cap ; t, root-cap, (x -J40.) 



parallel to its base. It is from the further division of these latter 

 cap-like segments that the ROOT-CAP is derived. In those ferns in 

 which the root may form a terminal shoot (p. 47) the apical cell of 

 the root according to the investigations of ROSTOWZEW ( 10;? ) forms the 

 apical cell of the new. shoot. It ceases to give off segments parallel 

 to the base, and the segments divide differently from those forming 

 the root. In the roots, as in the stems of the Lycopodinae, no apical 

 cells are found. In like manner the roots of Phanerogams, although 

 exhibiting several different types of apical growth, follow the same 

 law in the arrangement of their elements as the vegetative cones of 



