206 TEXT-BOOK OF FUNGI 



host-plant. Such may be briefly alluded to under two 

 headings. 



(1) Atrophy. Reduction in size or abortion of the 

 plant, or of special organs. Fungi causing this condition 

 of things have been termed Atrophytes. The stunted 

 leaves of witches' brooms illustrate the arrest of develop- 

 ment of a special part of the plant. A minute fungus 

 called Synchytrium, forming tiny galls on leaves of dande- 

 lion and other plants, prevents such leaves from attaining 

 the normal size. Sometimes the entire plant is much 

 stunted, as in the case of Euphorbia cyparissias when 

 attacked by the aecidial form of Uromyces pisi. Here the 

 stunting is so marked that there is not the slightest resem- 

 blance to normal plants of the same species. When 

 Agrostis vulgar is is infected with Tilletia decipiens the 

 whole plant is much dwarfed, and was at one time con- 

 sidered as a distinct variety called pumila. 



(2) Hypertrophy. An abnormal enlargement of an 

 organ or of the entire plant. Fungi causing such abnor- 

 malities have been termed Hypertrophytes. Members 

 of the Uredineae often cause a considerable increase in 

 size of the parts infected. Gymno sporangium causes 

 spindle-shaped swellings on branches of juniper, and also 

 very large barrel - shaped thickenings on the trunks of 

 various conifers. Galls reaching to the size of a cherry 

 are formed on the leaves of Rhododendron hirsutum by a 

 species of Exobasidium. Branches of Acacia horrida are 

 much swollen and twisted into most fantastic shapes by a 

 fungus called Aecidium ornamentale. Ustilago cruenta 

 causes the stem of Zizania latifolia to become swollen 

 and succulent, and in this condition it is sold -as a 

 vegetable in China. In Northern Europe young shoots 



