272 MOSSES AND FERNS CHAP. 



four together, with the sporangia close below them (Fig. 141, 

 D). This at first sight looks as if the sporangia were produced 

 upon the lower side of these, like Equisetum, but a very slight 

 examination shows at once that this is only apparent, and the 

 sporangia are undoubtedly outgrowths of the branches as in 

 Botrychium. The green lobes are seen to be only the vegetative 

 tips of the branches, or perhaps better comparable to such sterile 

 leaf segments as are not uncommon in Osmunda Claytoniana. 

 (Bower (17), Goebel (22), p. 664.) 



The sporangiophore in Helminthostachys originates as in 

 the other genera, and is bent over and protected by the sterile 

 leaf-segment, very much as in Botrychium. There is a certain 

 correspondence between the early stages of the sporangiophore 

 of Helminthostachys and that of Ophioglossum, but in the 

 former there are later developed short lateral outgrowths, or 

 secondary sporangiophores, which bear clusters of sporangia 

 more like those of Botrychium, but the pinnate form of the 

 sporangiophore is much less evident. 



The young sporangia project less than those of Botrychium, 

 but otherwise closely resemble them. The archesporium is 

 referable to a single mother-cell, but the tapetum is derived from 

 the surrounding tissue, and not from the primary archesporium, 

 as in Ophioglossum. Some of the sporogenous cells, as in 

 Ophioglossum, become broken down. 



