222 



PLANT LIFE. 



316. Simple sporangia.- -The simple sporangium may 

 be like the general body-cells, or it may be specialized in 



FIG. 220. 



FIG. 220. Longitudinal section of the simple sporangium of a mold (Mucor). The 

 aerial hypha, /i, has partitioned off a cell, -r, within which spores are produced. The 

 walls of this sporangium are studded with needle crystals of calcium oxalate. The par- 

 tition protrudes far into the end cell. Magnified 260 diam. After Kerner. 



FIG. 221. Longitudinal section of the stem, j, of a moss gametophyte, bearing leaves, 

 b. Embedded in the stem is the sporophyte, consisting of a stalk, -y/ 1 , and a compound 

 sporangium, of which tv is the wall, formed ot a sheet of cells, enclosing the spores, 

 j/ (contents not shown). Magnified 100 diam. After Hofmeister. 



form as well as in function. It may be spherical, sac-like, 

 or linear. The elongated sporangium produced by the en- 

 largement of the end of a hypha in certain fungi has received 

 a special name, ascits. The number of spores formed within 

 a simple sporangium may be two or more, up to several 

 hundred. The spores are formed like the zoospores de- 

 scribed in ^[ 306, with the difference that a wall is secreted 

 by each spore before it escapes. 



The rupture of the cell-wall, which sets the spores free, 

 is brought about by the increase of the spores in size, or by 

 the swelling of the surplus protoplasm left after their forma- 

 tion. Preparatory to bursting, the wall is frequently altered 

 so as to be mucilaginous, or it becomes brittle. In some 

 cases a certain area is thin, which furnishes a starting-point 

 for the rupture. 



