PTERIDOPHYTES 



107 



sporophylls is the strobilus (Figs. 75 and 81), and it is a very 

 important structure, for it is the precursor of the flower. 



In general, the Club-mosses have strobili very distinct from 

 the rest of the body (Fig. 75), for they are borne at the ends 

 of the vertical branches, and are often stalked far above the 

 foliage-bearing part of the stems. It is 

 these strobili that are the " clubs" of the 

 Club-mosses, a name which may now be 

 interpreted as meaning moss-like plants 

 that bear clubs. It must be kept in mind 

 that in these strobili of Club-mosses, each 

 sporophyll bears a single large sporangium 

 on its upper surface near the base, and 

 that a strobilus is simply the tip of a stem 

 (or branch) bearing sporophylls so close 

 together that they overlap. 



The Equisetums also have strobili (Fig. 



FIG. 87. Equisetum: A, a single sporophyll, showing the 

 peltate top from which the sporangia hang; B and C, 

 spores showing the unwinding of the peculiar bands that 

 form the outer coat. 



FIG. 88. Ophio- 

 glossum (adder's 

 tongue) : a fern 

 with a part of 

 the leaf bearing 

 sporangia. 



81), and the sporophylls are very different from those of the 

 Club-mosses, for each sporophyll is a stalk-like structure 

 with an expanded top (" peltate "), from the under side of 

 which several sporangia are suspended (Fig. 87). 



The Ferns do not have strobili, although in some of them 

 there are sporophylls distinct from foliage leaves, and in more 



