vii PTERIDOPHYTA—FILICINEJE—OPHIOGLOSSACEJE 247 



diameter show a somewhat similar arrangement of the vascular 

 bundles, but here there are free branches extending between the 

 sporangia. The relations of the bundles of the fertile and sterile 

 parts of the leaf are best 

 followed in the smaller 

 species. Prantl ((7), p. 

 155) describes it as fol- 

 lows for O. Liisitaiiininij 

 and states that it is essen- 

 tially the same in other 

 species. ''The primary- 

 bundle given off from the 

 stem branches just after it 

 enters the petiole. The 

 main bundle gives off two 

 smaller lateral branches 

 right and left. The latter 

 branch again near the base 

 of the sporangiophore,and 

 the upper branches from 

 each unite to form the sin- 

 gle bundle that enters the 

 latter." 



The sporangia are 

 sunk in the tissue of the 

 sporophyll, and scarcely 

 project at all above the 

 surface, where the position 

 of each one is indicated 

 by a faint transverse fur- 

 row which marks the 

 place where it opens. 

 Seen in sections parallel to 

 the flat surface these ap- 

 pear perfectly round, but 

 in transverse section are 

 kidney-shaped (Fig. 

 140, C). 



The apex of the stem forms a blunt cone, which, however, is 

 not visible from the outside. A longitudinal section through 

 the end of the stem shows that it is covered by a sheath com- 



FiG. 132. — Ophioghssum vulgatum, Xi. 



