SEXUAL REPRODUCTION. 



279 



that for the ovaries (fig. 326). (See also fig. 42.) The 

 sperms are set free by the rupture of the wall of the spermary. 

 382. A compound spermary consists of one or more cells 

 in which the sperms are to be produced (each corresponding 

 to a simple spermary), surrounded by a wall formed of a 

 single layer of cells (rarely more). Compound spermaries 

 are found only in Characeae, mossworts, and higher plants. 

 The spermary is a spherical or elongated sac, raised upon a 

 stalk, or sessile ; free upon the surface of the plant, or sunk 

 in a pit (fig. 311). The cell in which each sperm is formed 



Fig. 311. — A, a longitudinal section ot a male head of Marchantia. t, portion of 

 thallus ; ha, enlarged head or receptacle; a, spermaries, sunk in pits opening at o. 

 Magnified about 15 diam. B, compound spermary. iu, its wall, surrounding the 

 immense number of minute regularly arranged sperm mother cells ; st, its stalk. 

 Magnified about 80 diam. — After Sachs. 



is called a "sperm mother cell." Each contains a single 

 nucleus which enlarges to form the sperm of that cell (fig. 

 312). The sperms are set free by the breaking down of the 

 walls of the mother cells at about the same time that the 

 outer wall of the spermary is ruptured by the destruction of 

 one or more of its cells. 



The form of the vegetative body of the gametophyte in all 



