40 STRUCTURE AND LIFE-HISTORY OF HAY-SCENTED FERN. 
the first leaf the stem is protostelic. It contains a solid core of scalariform 
tracheids (xylem), surrounded in succession by conjunctive parenchyma, 
phloem, pericycle, and endodermis (fig. 238). At the exit of the first 
leaf-trace there is a depression containing parenchyma on that side of the 
xylem (fig. 239). Farther up the xylem extends around so as to inclose 
this parenchyma. In the parenchyma, even before the exit of the second 
leaf-trace, phloem and conjunctive parenchyma may be recognized (fig. 
240). The second leaf makes a similar gap in the xylem. Between the 
second and third leaf-gaps there appears in the midst of the central phloem 
a group of large cells identical in appearance with the outer pericycle (fig. 
241, 7). At the exit of the third leaf-trace the outer pericycle becomes 
continuous with the central tissue just mentioned, through a gap in the 
xylem and phloem (fig. 256). The gap closes again without any dipping 
in of the endodermis. Below the fourth leaf there appears a thickened 
band (Caspary’s band) on the cross wall between two parenchyma cells at 
the center of the stele (fig. 242). In the next section (10 » higher) there 
is a line of five cells whose intermediate walls bear the thickened band 
characteristic of endodermis (fig. 243). Two sections higher (20 #) there 
is a ring of endodermis at the center of the stele, inclosing one scleren- 
chyma cell (fig. 244). The ring enlarges rapidly and parenchyma cells 
appear beside the sclerenchyma (fig. 245). The solenostelic structure is 
established. The fourth leaf-gap is like the third, with only a very slight 
dipping inward of the outer endodermis (fig. 257). Only at the fifth or 
sixth gap, 7. e., above the fork of the stem, is there a continuity established 
between inner and outer endodermis and between medulla and cortex, as 
in the adult plant. The above description is of an average case. The 
exact position of each stage differs according to the size of the individual 
sporeling. The whole course of development is remarkably identical with 
that described by Boodle (1901) for the early stages of 4neimia phyllitidis. 
Dennstedtia stops at the solenostelic stage, while Axeimia goes on to 
become dictyostelic. 
To the practiced eye the first leaf of a young fern is often sufficient to 
distinguish the species. In any case the third, fourth, or fifth leaf will 
bear undoubted specific characteristics. The first leaf of Dennstedtia 
punctilobula is usually two-parted, with each part bifid at the apex (figs. 
259, 267). In more slender examples the two lobes are narrow, elliptic, 
and entire. I have seen two cases where the leaf bore but one elliptic 
entire bit of lamina. The average leaf measures 0.32 cm. to 0.38 cm. 
across. Its venation is simply forked. In the bud it is folded over at the 
tip in involute manner, but could hardly be called circinate. The same is 
true of the rudiment of the second leaf. The second leaf is also broad 
and lobed. It has three or four main lobes, each bifid or emarginate at 
apex. It is larger than the first, being 0.46 to 0.81 cm. in width and 0.4 
cm. or less in length (figures 260, 261). The third leaf is pinnately 
