THE FERNS 



537 



the lowest cell gives rise to the first leaf. A later stage in the de- 

 velopment of these parts is shown in Fig. 36.5, B. Covering the 

 growing tip of the root, somewhat as a thimble covers a finger tip, 

 is a protective organ termed the root-cap. Such a thimble-like cover- 

 ing continually renewed by the meristem which it protects is char- 

 acteristic of true I'oots. Root-hairs for absorption are soon devel- 

 oped. The leaf (Figs. 365, B, 362, B) soon differentiates into petiole 

 and blade, and cur^-es so as to drag the tender leaf-tip up out of 

 the ground. An extreme curvbig of this nature performed by t'very 



Fig. 363. — Fern Antheridium iPtcris i/;.. Polypody Family, Polypodiacew), 

 "i". (Lucrssen.) 



Fig. 364. — Fern Archegonium {Osmunda .sp.. Royal-fern Family, Osmunda- 

 ceai). A, first stage viewed from above, ^^-. B, same, cut vertically to 

 show the central cell (c) from which the egg is formed, and the cells (h) 

 which give rise to the neck, i;!". C-E, older stages, showing canal 

 cells (Ac, 6c). F, neck with mouth closed. G, same, top view, /f, same, 

 mouth open. /, same as E but w'ith egg-cell (f) ready for fertilization. 

 (Luerssen.) 



branch of the developing leaves gives us the familiar crozier-Iike 

 vernation characteristic of ferns. In the axis of the stem soon ap- 

 pears a central cylinder of prosenchyma which developing also in 

 the root and the leaf serves as a channel for conducting solutions 

 absorbed bj^ the root to the green food-making parts of the leaf, 

 and likewise dissolved nutrients from the leaves to the stem and 

 the root where they may be used in growth or stored as a reserve. 

 As the stem grows larger, and leaves and roots become more numer- 

 ous, its central cylinder becomes a hollow cylindrical net-work of 

 broad fiat meshes (Fig. 366), giving off slender branches to the 



