SYMBIOSIS. 339 



general, according to the circumstances. Many animals are 



Fig. 379.— Roots of a yellow Gerardia, G, attached to the root of a blueberry bush, B. 

 They enlarge at the points of contact and there send haustoria into the host root. 

 Natural size.— After Gray. 



thus preyed upon by bacteria and fungi. Most communi- 

 cable diseases, such as typhoid fever, diphtheria, and tuber- 



n dodder twining about a hop stem. All but the uppermost coils 

 show the groups of wartlike swellings trom whi< h haustoria pi ni trate the host stem. 

 Natural 51 v : I ■■ rm nation ol ame. Thi are arranged in ordi 1 



from right to left, tn the lasl ound a suitable support and has 



absorbed all the reserve food in the thicl nd, which has withered and died, 



freeing the plant from the ground. Magnified 1 Vfter Kerner. 



