348 GENERAL PLANT PATHOLOGY 



leaves approximately horizontal. When attacked by a rust fungus, 

 Endophyllum sempervivi (Fig. 137), the diseased leaves grow erect. 

 The same is true with our native American hepatica, Hepatica triloba. 

 Infrequently, it is attacked by a rust fungus in the aecial condition, 

 Tranzschdia punctata, so that (Fig. 138), the rusted leaves develop a 

 larger, stiffer petiole, stand erect with a smaller, stiffer leaf blade on 

 which the aecia are found. The common garden purslane Portulaca 

 oleracea, usually grows in a prostrate position, but when attacked by 

 the white rust, Cystopus {Albugo) porttdaca, many of the diseased 

 branches become erect or ascending. The stems of Vaccinium vitis- 

 idaa become erect the second year after infection by Mdampsora 

 Goeppertiana. 



Fig. 137. — Two plants of house-leek. Sempervivum. Left one affected bv Endo- 

 phyllum sempervivi. Right one. a healthy plant. (After Grove, W. B.: The British 

 Rust Fungi, 1913: 54. 



10. Destruction of Organs. — The destruction of plant organs by the 

 attack of fungi is well illustrated by the cereal smuts, which attack the 

 flower parts reducing them to a black powdery mass of spores, which are 

 carried away, leaving nothing but the bare axis on which the flowers 

 were originally situated. 



11. Excrescences and Malformations. — These will be treated of in 

 detail in another chapter. Here it may be said that galls, pustules, 

 tumors, corky outgrowths, crown galls, cankers, burls, or knauersi 

 (Fig. 139) witches' brooms (Fig. 140), etc., are evidences of diseased 

 conditions. The nature of these excrescences and maUormations can- 

 not be discussed here, but it may be said that they are specific and 

 usually associated with the attack of some fungus, as for example the 

 plum knot due to Plowrigktia morbosa, the cedar apples formed on the 



