VEGE TA 7V I 'E REP ROD UCTION. 



221 



tubes on the under face, as in Poly /writs (fig. 218) ; or it may 

 take the form of a ball, the hymenium arising as a lining 

 upon the walls of regular or irregular internal chambers, 

 which may occupy most of the interior, as in puff balls and 

 their kin (figs. 214, 219). 



315. Sporangia. Spores are also formed in the interior 

 of cells which are either free or covered by a jacket of other 



FIG. 219. Fructification of a puffball (Geaster hygrometricus) ; A, young; B, mature, 

 the outer layer split open and recurved, the inner also broken to allow escape of 

 spores. Natural size. After Corda. 



cells. The entire structure is called a sporangium. In the 

 first case the sporangium is said to be simple. Its wall is the 

 wall of the mother cell in which the spores are produced, 

 and they are set free by its rupture (fig. 220). In the second 

 case the sporangium is said to be compound. The mother 

 cells of the spores (rarely only one mother cell) are sur- 

 rounded by others forming a jacket of greater or less thick- 

 ness. In the mother cells, which are differentiated from the 

 investing cells, the spores are formed as in simple sporangia. 

 As the spores mature the walls of the mother cells burst or 

 are disorganized, leaving the spores still surrounded by the 

 layer or layers of investing cells (fig. 221). This jacket is 

 ruptured sooner or later and the spores, thus set free, are 

 distributed in various ways. (See T 475- ) 



