64 THE OPHIOGLOSSALES 



time the section of the stele appears perfectly circular and continues downward 



until it reaches the next leaf trace, which marks the point of departure of the 

 trace of the cotyledon. Except for the greater development of the xylem, which is 

 composed ot two to three concentric rows of tracheids, the section of the stele in this 

 region presents much the same appearance that it does in tin- younger pairs nearer 

 the stem apex. The outer part of the stele at this point shows a somewhat broken 

 row ot thick-walled hast fibers within which are large sieve tubes. I he cambium, 

 lying just inside the phloem, is very much less developed in the basal region of the 

 stele than it is higher up and can scarcely he said to he present. The stele in this 

 region ot the stem is quite similar to that of B. lunar i a, figured by Poirault. The 

 endodermis is also much less definite than it is later, and I could not satisfy myself 

 that there was in B. virginianum any trace of the inner endodermis which Poirault 

 states is present in the basal part of the stem in B. lunaria, hut which disappears 

 later. The medullary rays also, which are conspicuous in the stele of the older 

 plant, are very imperfectly developed in this basal legion. 



In the intermediate region, between the base of the primary root and the trace 

 from the cotyledon, a section shows a thick irregular ring of tracheal)' tissue with 

 no clearly developed medullary rays (fig. 43, L). Indeed, at the lowest part of this 

 region the tracheary tissue forms an almost solid core with only a small amount of 

 parenchyma interspersed, thus forming an inconspicuous and irregular pith. While 

 the endodermis is not clearly delimited, some of the cells in the zone of tissue sur- 

 rounding the stele show the radial thickenings of the walls; but these cells are not 

 all of them in the layer immediately adjoining the stele, being irregularly disposed 

 throughout the three or four layers of cells surrounding the stele. As sections are 

 examined in succession upwards, the pith becomes better defined. Sections taken 

 downward show a ring of tracheary tissue gradually separating into the two or three 

 xylem masses of the primary root. 



The primary root in the sporophyte which has just been described was diarch. 

 The stele shows a very evident endodermis, within which is the pericycle, for the 

 most part composed of two layers of cells. The xylems are composed of a large 

 group of tracheids, of which the two or three smaller ones next the pericycle repre- 

 sent the protoxylems. Small, deeply staining protophloem elements can be seen 

 toward the outside of the phloem, and within these are the other phloem elements, 

 thick-walled bast fibers, and sieve tubes. The rest of the stele is composed of small, 

 thin-walled parenchyma cells. The outer region of the root is made up of somewhat 

 compressed cells suggesting the periderm cells which are found in parts of the older 

 stem and which are also present in the cortex of the later roots. This outer layer of 

 cells, however, shows no evidence of active division. 



A cross-section of the petiole of the cotyledon, from the same sporophyte, taken 

 at a point some distance above the stipules, shows within the epidermis about three 

 layers of parenchyma cells with no conspicuous intercellular spaces, but within 

 these are several very large lacuna?, separated by narrow plates of tissue. In the 

 center of the section are seen the two concentric bundles that traverse the petiole. 

 As in the later leaves of this species, these bundles are truly concentric, thus resem- 

 bling those of the Marattiace.e and differing from the collateral bundles of Ophio- 

 glossum and the smaller species of Botrychium. I In phloem is better developed 

 upon the outer side and small protophloem elements can be seen at its outer limit, 

 but these are continued partially around the inner side of the bundle, where the 

 xylem is separated from the outside by about two layers of cells. No definite 

 endodermis can be made out. The two bundles are continued up to the base of the 

 lamina, where one of them passes into each lateral lobe of the ternate leaf. One of 



