XII 



LEPTOSPORANGIA T.E HETEROSPORErE 



399 



and in M. JEgyptiaca the writer has found a two-celled embryo 

 developed within thirteen hours from the time the ungerminated 

 spores were placed in water. 



The sporocarp of Marsi/ia is a bean-shaped body, which is 

 attached to the petiole of the leaf by a more or less prominent 

 pedicel. It is very hard, and unless opened artificially may 

 remain a long time unchanged, if placed in water ; but if a 

 little of the hard shell is cut away, the swelling of the interior 

 mucilaginous tissue quickly forces apart the two halves of the 



Fig. 206. — Marsilia vestita (Hook and Grev.). A, Fruiting plant of the natural size; sfi, 

 sporocarps ; B, a single sporocarp, X4; C, cross-section of the same, X 5 ; D, germinating 

 sporocarp, showing the gelatinous ring by which the sori (.r) are carried out, x 3. 



fruit. As more water is absorbed, this gelatinous inner tissue 

 continues to expand and forms a long worm-shaped body (Fig. 

 206, D), to which are attached a number of sori, each surrounded 

 by a sac-shaped indusium in which the sporangia are closely 

 packed. Macrosporangia and microsporangia occur in the 

 same sorus. The former contain a single large oval white 

 spore, the latter much more numerous small globular ones. 

 The indusium remains intact for several hours, if not injured, 



