DEVELOPMENT OF PLANTS 



315 



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- 

 tures that recall the sporophyte of Anthoceros (Figs. 215, B\ 

 199). The outer portion of the cylinder consists of chlorophyll- 

 bearing cells which communicate with stomata in some of the 

 forms at least. The spore mother cells are also distributed as 



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, Botrydmim. 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. 



in Anthoceros, the essential difference being that they are sepa- 

 rated by a larger number of sterile cells and a larger number of 

 spore mother cells are also grouped together, forming rather con- 

 spicuous sacs or sporangia (Fig. 215, sp). The spores are formed 



