MARSILIA VESTITA. 185 



able still further to advance our knowledge of the early 

 stages. Still there were several points in regard to Mar- 

 silia that were obscure, especially the first divisions in 

 the prothallia, and these it was possible to clear up by a 

 study of the material at my disposal. 



THE FRUIT. 



The sporangia of the Marsiliacea? are formed within 

 peculiar " fruits " which are modified segments of 

 the leaves, bearing much the same relation to the 

 sterile portion that the fertile segments of the leaves of 

 Botrychium or Osmunda do to the sterile ones. These 

 sporocarps in Af. vestita (pi. in, fig. i), are bean shaped, 

 very hard bodies, about five mm. in length, and attached 

 to the base of the petiole. They are more or less hairy, 

 whence the specific name. These fruits open sponta- 

 neously when perfectly ripe, if placed in water, but the 

 process Is comparatively slow and may be hastened bv 

 cutting away enough of the hard outer shell of the fruit 

 to expose the yellowish inner tissue. This latter is of a 

 mucilaginous nature, and on the absorption of water 

 swells up enormously and causes the two halves of the 

 fruit to separate as two valves. The gelatinous inner 

 tissue of the fruit continues to expand as more water is 

 absorbed, and finally forms a long worm-shaped bodv, 

 sometimes eight or ten cm. in length. To this are at- 

 tached the sori, each surrounded by a sac-shaped in- 

 dusium, in which the sporangia are closelv packed (pi. 

 Ill, fig. 2). Both sorts of sporangia occur in the same 

 sorus. Each macrosporangium contains a single very 

 large macrospore ; the microsporangia numerous much 

 smaller microspores. If care is taken in opening the fruit, 

 the indusium remains intact for several hours, and this 

 was found a great help in the study of the microspores. 



