VEGETATIVE RETROD UCTIO.V. 



223 



; 3 J■i:^-i.''^i,^.\ 



317. Arrangement. — Simple siiorangia may occur singl}- 

 or they maybe aggregated. A\'hen 

 aggregated, they usually stand side 

 by side, and constitute a layer, 

 called the hymeniiim (figs. 222, 

 226). (Compare •[ 314.) When 

 thus aggregated (and even when 

 single) they may be enclosed by 

 a jacket formed by the coalescence 

 of sterile filaments, as in the mil- 

 dews, in which the whole structure 

 constitutes a fructification (figs. 



23. 224, 



In the lichens the 



hymenium, during its earlier stages, 

 is partially enveloped by sterile 

 filaments forming a cup-like apo- 

 ikeciu?n (figs. 225, 226). In the 

 cup fungi (fig. 222 ) the fructifica- 

 tion, which is the only part of the 

 fungus above the substratum, is a 

 single apothecium, whose whole 

 inner face is the hvmenium. In 

 an allied form, the morels (fig. 



Fig. 222. — A cup fungus iPeziza 

 :2ura7iiia). A, three fructifica- 

 tions, about natural size. The 

 inner surface of the cup is co\ered 

 with a liymenium, a bit of \\'hich 

 227), the IrUCtlllCatlOn is differ- is shown at a in section at right 



angles to surface. /, paraphyses ; 

 It, an ascus bursting to allow 

 escape of spores. Highly magni- 

 lied. — .^fter Kerner. 



The hymenium extends 



entiated into a stalk carryiug an 



enlarged head marked hv narrow 



ridges separating broad shallou- pits 



over the surfiice of these depressed areas. In other fungi, 



the sporangia are sunk in deep, narrow-mouthed pits with 



x-i-hich the outer part of the fructification is filled (fig. 22S). 



The simple sporangia of some of the red seaweeds show a 

 transition to the compound type in being formed by an in- 

 ternal cell of the thallus (fig. 229). The adjacent cells, how- 

 ever, do not constitute a special wall, nor are they neces- 



