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 

 erenated (figs. 262, 263). The fourth and succeeding leaves are pinnate 

 like the third, but with more pinnae (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 pinnae 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 imder- 

 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, w) 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 on the 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. 



I 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. 



