. Carnegie Institution of Washington publication. 78 1111 OPHIOGLOSSALES the protoxylem .1 few scattered, large tracheary elements, so that the bundle may he to be mesarch, .is Farmer states is the ease In the older rhizome. During its earliei stages the stele shows no leaf gaps where the leaf traces depart, and the leal gaps are only gradually developed. Soon after the stele has assumed the form of a hollow cylinder the leal gaps are for some time absent, or thev are developed onlv in a \ei\ small degree and close almost immediately upon the departure of the leaf trace. In none of the y
. Carnegie Institution of Washington publication. 78 1111 OPHIOGLOSSALES the protoxylem .1 few scattered, large tracheary elements, so that the bundle may he to be mesarch, .is Farmer states is the ease In the older rhizome. During its earliei stages the stele shows no leaf gaps where the leaf traces depart, and the leal gaps are only gradually developed. Soon after the stele has assumed the form of a hollow cylinder the leal gaps are for some time absent, or thev are developed onlv in a \ei\ small degree and close almost immediately upon the departure of the leaf trace. In none of the young plants that I examined could I detect any of the inner endodermis which occurs in the older rhizomes. Farmer, however, states that the inner endodermis is only imperfectly developed and concludes that it is the result of the- invagination of the outer endodermis through the leaf gap; or, to put it in another way, it is the persistence of the inner endodermis of the leaf traces of which the hollow stele is made up. The bundle at this stage most nearly resembles that of Botrychtum lunarta, differing from that of B. virgimanum in the absence of a true. Fig. 52. A. Section d( tin ^oung central stele of Hrlminthoitachxs, showing tin' two xylems. X200. IS. Stele from lower part of .in oldei sporophyte, showing junction of a leaf trace with central 6tele. X50. C. Part of central stele, more highly magnified. cambium, the outer wood cells being directly in contact with the inner cells of the phloem. Occasionally, however, there may be seen on the outer edge of the xvlem ring a few imperfectly developed tracheids which probably represent a very rudi- mentary development of secondary wood, but there is no other sign of the definite cambium /one which is so conspicuous in the stele of Botrychtum virgimanum. From this study of the development of the leaf traces, following them from the stem apex downward, it appears that the cylindrical stele in Helmtnthostachyi arises in precisely th
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