292 GENERAL BIOLOGY 



Especially is this true of the fungi. Fungus spores of 

 various sorts fall upon leaves or stems of a green 

 plant, and germinating, gain access to the interior 

 through stomata or injuries in the bark or by directly 



FIG. 106. A, European dodder twining about a hop stem. All 

 but the uppermost coils show the groups of wartlike swellings from 

 which haustoria penetrate the host stem. Natural size. B, germination 

 of same. The various stages are arranged in order from right to left. 

 In the last stage the seedling has found a suitable support and has 

 absorbed all the reserve food in the thickened lower end, which has 

 withered and died. Magnified about two diameters. (From Barnes, 

 after Kerner.) 



dissolving the outer -tissue, and, once gaining a 

 foothold, grow and ramify in all directions, producing 

 blight, rot, or abnormal growths (tumors). Familiar 

 examples are the " rust " and " smut " of wheat 

 and corn. 



