EFFECT OF I'AKASITIC Ft'Nu'I ON THE FoKM OF II' 1 -1'LANT. 25 



FII;. 7. Fruit "f j>lum <K-f.'niH-'l \>\- 



the ovules become atrophied, whereas tlie rest of the llower 

 is hypertrophied. Similarly \vilh 

 flowers of cowberry deformed by 

 Exobasidium. 



'1. Hypertrophy. .Many para- 

 sitic fungi cause abnormal enlarge- 

 ment or other malformation of 

 plants which they attack. The 

 -implest case of hypertrophy is 

 seen in the enlargement of a uni- 

 cellular plant as a result of an 

 endophytic parasite, <.</. /Y/"W//.s 

 Kl'iiiii with I'liotrix'li'ln*. 



The same example is also the 

 simplest possible case of a gall 

 caused by a plant, and distin- 

 guished by the name of "fungus- 

 galls'' or Myeocecidia, from /ooce- 

 cidia, the galls caused by animals. 

 Lir-er galls occur >n leave- 

 attacked by /S'///<r//////-//////, where 

 not only the single cell attacked 

 becomes enlarged, but also the surroundinu cells: these galls, 

 however, form but tiny points on diseased leaves. Similar 

 small and local enlargements ,,f the leaf-cells, accompanied 

 frequently by cell multiplication, are caused by many other 

 fungi, - .'/. species of KI-OHXI-U*. More extensive malformatioD may 

 embrace some part or even the whole leaf, so that it is more 

 or less enlarged and beset with blister-like outgrowths, as \\itli 

 other Exoasceae (see Fii:-. Hi' and 04). <Hher gall-f'nns are 

 presented by _Vn//x/V /'///// nn the alpine-ru.-M- (Fig. l2."> ( ,i). where 

 tlie gall is always lneali/ed to a small area (if the leaf. ,md 

 in the cowberry, where the gall may extend over wlmle Leaves, 

 and even include the shoot (Fig. L'.'ii). 



Hypertrophy of the whole shoot, resulting in eloii-ai imi and 

 thickening of tlie twigs, is a phenomenon frequently met with 

 in the "witches' brooms," to be referred to later. And just 

 .1- entire branch-systni> may become hypertrophied and el.ui- 

 gated, 80 may whole plants, if the mycelium, instead of remaining 

 . spreads throicjlmiit the plant. F\am|iles of thi- will 



irtivc. v natural si/.o. (v. Tuln.-uf 

 phot.) 



