PLANT LIFE. 



occur, and a section of the resulting structure has much the 

 appearance of a section of the tissues of a higher plant (fig. 

 55). These changes are particularly apt to occur among the 

 superficial parts of the more massive structures among the 

 fungi, where they are necessary to impart firmness, rigidity, 

 or durability. For example : in the ergot, a fungus common 

 upon certain grasses, a portion of the mycelium is to survive 

 the winter and grow again the next season. This portion 



rn 



FIG. 54. FIG. 55- 



FIG. 54. Branching haustoria of Peronospora. m, m, the hypha traversing an 

 intercellular space of the host ; z, z, two haustoria penetrating two cells of 

 the host and branching therein. The other contents of host-cells not shown. 

 Magnified about 400 diam. After De Bary. 



FIG. 55. A section through the mycelium of a lichen showing hyphse near upper sur- 

 face, a, and lower surface, b, fused into a false tissue ; only in central region are the 

 filaments recognizable. The dark spheres are imprisoned algae. Magnified 650 diam. 

 After Bornet. 



replaces the young ovulary of the flower (see 1~ 335), and, 

 as it matures, becomes a dark-colored mass, as firm and re- 

 sistant as the grain itself (fig. 56). 



The interweaving and fusion of the hyphae sometimes pro- 

 duce cord-like or strap-like structures of considerable size. 

 The mycelia of the higher fungi frequently form them, and 



