300 



THE OPHIOGLOSSALES 



and leaves of the same tissues that we have noted in the higher 

 seed plants. The vascular bundles are usually collateral and in 

 the larger species of Botrychiiim are arranged in the stem in a 

 circle and provided with a cambium, so that there is a striking 

 resemblance to the dicotyledonous stem with its pith, ring of 

 xylem, cambium and phloem, medullary rays, cortex, cork, etc. 

 (Fig. 216). 



Fig. 215. The two common genera of the Ophioglossales: A, the adder- 

 tongue fern, Ophioglossum, with single leaf ensheathing the short stem and 

 producing a spore-bearing spike. B, section of the spike — sp, the spore- 

 forming cells arranged in groups or sporangia. The spores are exposed by 

 the breaking apart of the cells between the dark lines. C, stoma from epi- 

 dermis of spike. D, the grape fern, Botrychiuni. The leaf is much divided 

 and also forms a branched spore-bearing organ. E, two sporangia, showing 

 the manner of opening for discharge of spores. 



The spores are borne in peculiar modified outgrowths of the 

 leaves that assume a cylindrical shape in Ophioglossum and be- 

 come more or less branched in the species of the Botrychium 

 (Fig. 215). The structure of these organs presents many fea- 



