THE OLDER SPOROPHYTE 



181 



at an earlier period. The mucilage ducts throughout the life of the sporophyte 

 are less conspicuous in Kaulfussia than in Dance a. 



A section taken at the level of the stem apex in the very young sporophyte 

 (fig. 137) presents an appearance not unlike that found in the bud in Ophioglossum. 

 The base of the cotyledon extends around the stem apex, so that in the section the 

 stem apex and the second leaf are inclosed in this cavity formed by the stipular 

 sheath of the cotyledon. Higher up, the base of the cotyledon becomes free from the 

 second leaf, but this takes place earlier on one side than on the other. 



The development of the vascular system in the stem is exactly as it is in Dancea. 

 The stem apex in the young sporophyte takes no part in the development of the 

 vascular bundles, the stele in the stem being made up entirely of the united leaf 

 traces. In the specimen figured (fig. 164), in which the second leaf was still quite 

 young, the bundle from the cotyledon passes downward into the stem and continues 

 its downward course until it joins the second leaf trace. The resulting solid stele 

 at first shows the two separated xylems of the component leaf traces which lower 

 down merge into a single thick band of xylem completely surrounded by the phloem 



Fk;. 1C5. — Three longitudinal sections of a young sporophyte of Kaulfussia, with three leaves. X25. 



(fig. 164, EH). This stage corresponds to Brebner's "haplostele" in Dancea sim- 

 plicifoha. This condition merges insensibly into the primary root with its diarch 

 bundle, the two xylems in the younger part of the root being quite separate, but 

 forming a single band at the base of the transitional region, between the root and 

 the bundle in the stem. The bundle of the root shows a conspicuous endodermis 

 which becomes less and less evident in the transitional region, although it prob- 

 ably never quite disappears. The primary root usually shows the presence of an 

 endophytic fungus like that occurring in the prothallium and in the primary root 

 of most of the Ophioglossaceae. 



Fig. 166 shows cross-sections of a young sporophyte in which the fifth leaf is still 

 quite small, but with its trace showing the first tracheary tissue. This fifth leaf trace 

 unites below with the trace from tin- fourth leaf and forms :i single bundle, with 

 the xylems separate. The xylem from the fourth leaf above its junction with the fifth 

 leaf trace forms at first a continuous band which divides into two parts, one of which 

 unites with the xylem from the fifth leaf trace, while the other remains distinct. 

 This separation of the xylem in the fourth leaf trace is the first indication of the for- 

 mation of tlu- double leaf trace, such as we shall find occurs in the later leaves. 



