VII PTERIDOPHYTA—FILICINE^—OPHIOGLOSSACEJE 271 



mediate between the other two, but differs from both in some 

 particulars. The sporophyte has a creeping fleshy subterranean 

 rhizome, with the insertion of the leaves corresponding to Ophio- 

 glossum pendulum. According to Prantl (7), who has made a 

 somewhat careful study of a plant, the roots do not show any 

 definite relation to the leaves, as Holle claims is the case in the 

 other genera. The plant sends up a single leaf, which may 

 reach a height of 30 to 40 cm. or more, and as in the Ophio- 

 glossum vulgatum and B. Virginianum, the sporangiophore 

 arises from the base of the sterile division of the leaf. The 

 latter is ternately lobed, and the primary divisions are also 

 divided again. The venation is different from that of the other 

 Ophioglossacese, and is extremely like that of Angiopteris or 

 Dancsa. Each pinnule is traversed by a strong midrib, from 

 which lateral dichotomously branched veins run to the margin. 

 In regard to the structure of the sheath that encloses the young 

 leaf and stem apex, Helminthostachys resembles Botrychium. 



The apex of the stem, as in the other genera, grows from a 

 single initial cell. The stem has a single axial stele, with the 

 form of a hollow cylinder, interrupted upon the upper side by 

 the leaf-gaps. In the youngest stems, the stele is solid. There 

 is an imperfect inner, and a distinct outer endodermis. The 

 xylem is mesarch — i. e., it begins to develop in the center of the 

 bundle — and its differentiation goes on very slowly. There is 

 no formation of secondary wood as in the larger species of 

 Botrychium. (Farmer (6)). 



The sieve-tubes have sieve-plates on their lateral faces, and 

 similar sieve areas occur upon the walls of the adjacent phloem 

 cells. The metaxylem has bordered pits, apparently similar to 

 those of Botrychium Virginianum. 



The roots resemble those of Botrychium. There are from 

 three to seven xylem masses. 



The sporangiophore is long-stalked and in general appear- 

 ance intermediate between that of the other genera, but a careful 

 examination shows that it is much more like that of Botrychium. 

 It is pinnately branched, but in an irregular way, and the small 

 branchlets bear crowded oval sporangia, which open longi- 

 tudinally on the outer side, and not transversely as in the other 

 genera. The tips of the branches, instead of forming sporangia 

 as in Botrychimn, develop into green leaf-like lobes, which upon 

 the shorter branchlets are often arranged in a rosette of three or 



