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, if>). 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 p- 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, /. 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 Aiiciinia fihyllitidis. 

 Dennstcedtia stops at the solenostelic stage, while Aneimia 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 Dennsteedtia 

 piiuctilobnla 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 lobcd. 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 



