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. 365, 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 roots. Root-hairs for absorption are soon devel- 
oped. The leaf (Figs. 365, B, 362, B) soon differentiates into petiole 
and blade, and curves so as to drag the tender leaf-tip up out of 
the ground. An extreme curving of this nature performed by every 
Fic. 363.—Fern Antheridium (Pteris sp., Polypody Family, Polypodiacee), 
359 (Luerssen.) 
Fic. 364.—Fern Archegonium (Osmunda sp., Royal-fern Family, Osmunda- 
cee). A, first stage viewed from above, 82. 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, 222. C—-E, older stages, showing canal 
cells (he, be). F, neck with mouth closed. G, same, top view. H, same, 
mouth open. J, same as E but with egg-cell (e) ready for fertilization. 
(Luerssen.) : 
gO 8 oe op VW Ress sy 
branch of the developing leaves gives us the familiar crozier-like 
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 by 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 flat meshes (Fig. 366), giving off slender branches to the 
