SECT. I 



MORPHOLOGY 



lOf 



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

 possess an apical cell in the shape of a three-sided pyramid (^**'') (Fig. 

 116 t). In addition to the segments given off by the apical cell 

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

 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 



Fii;. lliJ. — Median longitudinal section of the apex of a root of Pteris cretica. 

 t, Apical cell ; k, initial cell of root-cap; kn, root-cap. (x 240.) 



the root may form 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 the stems. It will, accordingly, 

 be sufficient to describe a root of one of the Graminae (Fig. 117) as a 

 representative of one of these types (^°^). The vegetative cone of 

 this root differs from that of the phanerogamic stem previously 



