THE YOUNG SPOROPHYTE. 41 
divided, with a comparatively broad, winged rachis. There are one or 
two pairs of pinnules and a terminal portion, all of which are lobed and 
crenated (figs. 262, 263). The fourth and succeeding leaves are pinnate 
like the third, but with more pinnz (figs. 264, 265). All of these early 
leaves are broadest at the base and they vary from deltoid to broadly 
lanceolate in shape. But in outline of the pinne and pinnules the third 
and fourth leaves are exactly like the mature leaf. They are thin and 
fragile, consisting only of upper and lower epidermis (figs. 254, 266) and 
one layer of spongy parenchyma (fig. 253). Stomata are numerous in 
the lower epidermis of each leaf, especially on the pinnate leaves. A few 
stomata occur scattered over the backs of the petioles (fig. 268). The 
margin of the leaf is strengthened by long, narrow, indurated cells under- 
lying the epidermis (fig. 251). 
The first two leaves are devoid of hairs of any kind. Hairs begin to 
occur on the third leaf, but the fourth shows three kinds of trichome struc- 
ture—glands, moniliform hairs, and acicular hairs. A few glands (fig. 
258, w) occur, thinly scattered on the upper and lower surfaces of lamina 
and rachis, but they are more plentiful on the petiole. Each one consists 
of one to three large, swollen cells. They probably represent the glandular 
hairs of the adult. Moniliform hairs (fig. 258, #) consist of three or four 
cells, each of which is broader above and narrower below. They lie 
appressed to the leaf-surface. They are plentiful on both surfaces of the 
lamina and rachis, but there are none at all onthe petiole. Acicular hairs 
like those of the adult leaf are plentiful all over the fifth leaf, and on the 
stem apex. They are four to seven cells long (commonly 4, 5, or 6), 
thick-walled, and curve outward from the surface of both the lamina and 
the petiole. 
The mature petiole of the early leaves is slender, flattened above and 
rounded below (fig. 248). Under an uneven epidermis there is a cortex 
composed of two or three layers of large, thin-walled cells. In this are 
large intercellular spaces. A well-defined endodermis demarcates a cyl- 
indrical vascular bundle. In this is a stout transverse band of xylem, 
surrounded by phloem and a single layer of pericycle. The xylem con- 
sists of narrow spiral and scalariform tracheids. 
As stated above, the first leaf is derived from two octants of the embryo, 
not from one alone, and grows always by a group of marginal initials. 
These undergo sectioning and halving as in the adult the leaves (fig. 250). 
The second leaf arises from the stem-tip. Its development has not been 
followed. 
J have not determined how long it takes to obtain mature plants from 
spores. Forked stems are found after about one year. In some cases 
certainly another season intervenes before maturity is reached. Probably 
they never fructify before the third or fourth summer. 
