nn: PATHOGENIC 1: M TKKIA. .V',1 



consider those phenomena. which h ;l \v 1 ..... n d<--> -iihed ;i s 

 bacterial diseases of plains, very briefly and wiili a certain 

 reserve. This part of the work ha- 1 ..... u considerably faciliuted 

 ly tlu- use ..f Ludwi-'s compilation of bacterial dia and l.y 



Migula's account of them from the bacteriological point of view. 



Mimila consider- that only live di- of plant- have 



definitely proved to he due to bacteria, namely, pear r apple 

 Illicit, -or-hum blight, the haeterial disease of bhe maize, tin- 

 ludb-rot of hyacinths, and the wet-rot uf potatoes. \\'f shall. 

 however, indicate 1'rietly some other plant di- which 



suspected to have a Kidi-rial ori-in. Tin- -limi--Iln\f- of i 

 have been already considered aloiiu with the -vnus Endom 

 (p. 141), so that we omit them here. 



Pear and Apple Blight. 



This destructive disease of the apple and pear in Xorth 

 America has been proved by the investigations ,,f I'.nrrill- 

 and Arthur to be, without doubt, of bacterial origin. The 

 disease has been known for over 100 years, and occurs 

 with disastnm- effects on fruit -trees in the orchard-, as well 

 as on crabs and other wild species. 1'ear trees seem to >ulfer 

 most in the Eastern States, apple trees in Iowa and elsewli 

 while none of the species of Pyrus, Cydonia, ami S are 



exempt from attack. 



The disease appears tir-t on the bark as little dead >p 

 these, however, rapidly imlaru'e till death of twins, hranchc-. ami 

 even stems may follow. A> a ivsull of death of twigS, ihe 

 Leaves turn brown and fall, while, a dark lluid e\ude< trom tin- 

 diseased bark. The presence of bactnia ha- be, MI pio\i-.l in 

 tin,- exuded sap a- well as insid" ih-- cells, and infections ha\e 

 been succes-fnlly carried out from pure cidtui The name 



M'I <,;,<,< u* miii/ln,-, ,,-,,,>* wa- -i\en by r.urrill to the op_r.ini-iii. 

 It lloiin-he- on the sour unripe fruit, and in the tissues "1 



1 /.'fn-liiii -It '/'i- !/> il< >< a AV ///''":/" '" :. 

 Mi.'ul.i, A ////'..//. Ueberyichl /. I'I/HH . > 



. Is'l'J. 



I'l illn-u\ i-i I >.-l.i.-i'ii\. \I ., i I vi| 



I', ii i ill, '/'/,. .1 /,/. rica A aturaliit, I ssi. 



\rilnir, /.' / \ ) I / - l^>7. 



VVaite, ) " '""/ "/ / '. >'. I > pt, ' 189 



t I i it lll>-llt. 



