38 



OUTLINES OF PLANT LIFE. 



mount and show the mycelium of the fungus consisting of tangled hyphse 

 ramifying among the cells of leaf. (TJT[ 44, 45.) 

 Examine a dried leaf. Observe 



2. The white blisters (sfore beds) here and there on the surface ; the 

 thin membrane (the epidermis of the leaf) by which they are covered ; 

 in older blisters the cracking and final disappearance of this skin. 

 (1 269, fig. 141.) 



3. The white powdery spores which jar out or can be dislodged vifith 

 needle. 



47. Fusion. — When the hyphae of a fungus grow very close 

 together, they frequently cohere and become so changed in 

 appearance as to lose all trace of resemblance to filaments. 

 Not only fusion but thickening and division occur, and a 

 section of the resulting structure has much the appearance of 



nrnr 



n 



Fig. 35. 



Fig. 36. 



Fig. 35. — Branching haustoria of Peronosporn. w, m, the hypha traversing an inter- 

 cellular 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. 36.— a section through the mycelium of a lichen showing hyphae near upper sur- 

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

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

 — After Bornet. 



a section of the tissues of a higher plant (fig. 36). These 

 changes are particularly apt to occur at and near the surface 



