I82 



MARSILEACEAE 



[CH. 



The sporocarp of Marsilea is constructed on the same plan, but with a 

 larger number of receptacles. The outline of it is seen from Fig, 464, A, 

 where the midrib, or "dorsal bundles" of Johnson, is directed upwards: from 

 it alternating veins arise, and they fork in their course towards the down- 

 ward-directed margin, within which the alternate strands fuse. The elongated 

 receptacles, constructed essentially as in Piliilaria, are borne between the 

 shanks of these lateral veins, and run transversely to the axis of the 

 whole sporocarp. A transverse section would then follow their course 

 (Fig. 465, A), and show the position of the sporangia with their heads 



fS^"'^ >.,^ 



Fig. 464. 



Fig. 465. 



Fig. 464. Marsilea quadrifolia. (After Duncan Johnson.) A, a view of the inner side of one of the 

 valves of a nearly mature sporocarp, slightly simplified. B, part of a horizontal section of a 

 receptacle, showing the relations of a megasporangium {ma), and the microsporangia {mi), and of 

 the indusium (i). 



Fig. 465. Marsilea salvatrix Hanst. A, transverse section of the ripe but still closed sporocarp. 

 ( X about 4.) g, g' , gelatinous ring : s, sorus. B, swollen and opened spore-fruit, with the swelling 

 gelatinous ring, g, which draws out with it the attached sori. { x about2i.) C, fully opened spore- 

 fruit, with the extended gelatinous ring, its ends still attached to the fruit-wall. The sori now free 

 are borne upon its dorsal side, while mammiform processes from which they have broken away 

 are seen on the ventral side. (Natural size.) D, a sorus magnified six-fold, with microsporangia 

 {mik), megasporangia [mak), and "indusium" {ids). (After Hanstein from Luerssen.) 



