PIT-CLOSING MEMBRANE IN OPHIOGLOSSACEAE 



Gertrude Wright 



(WITH PLATES XI, XII AND SIX FIGURES) 



The members of the Ophioglossaceae, an isolated family of un- 

 certain origin, are forms with a few large leaves, simple to decom- 

 pound, and short, slow growing, underground stems, vertical, 

 oblique, or horizontal in position, with crowded fleshy roots. The 

 leaves, which are divided into sterile and fertile lobes, bear on the 

 latter homosporous sporangia. 



Of the three widely distributed genera, Helminthostachys, a 

 monotypic genus, is the most restricted, occurring throughout 

 tropical Asia to North Australia and New Caledonia. Opkio- 

 glossum is represented by about 30 species growing under various 

 conditions of moisture and shade in the temperate and tropical 

 zones of both the Eastern and Western hemispheres. Botrychium, 

 with nearly as many species, is world wide in its distribution, but 

 is confined chiefly to the temperate regions. 



The forms considered in this paper are Helminthostachys zey- 

 lanica, Ophioglossum vulgatum, the only species of the genus native 

 to Canada, and Botrychium obliquum, one of the 6 or 8 forms found 

 in Ontario. 



The rhizome of Ophioglossum vulgatum consists of a large, 

 starch-filled cortex surrounding a siphonostele of endarch bundles 

 of primary wood. This cylinder may be broken by leaf gaps, 

 often so prolonged as to overlap, producing a circle of bundles. 

 Fig. 1 shows several such bundles, one, beside an outgoing root, 

 starting on its way through the cortex to the petiole. There is 



Helminth 



mature plant, and the 

 k. through the large leai 



presents a slightly different appearance in cross-section. Fig. 2 

 shows its broad woody cylinder solid on the lower side, broken 



237] 



[Botanical Gazette, vol. 69 



