34 



KK.UTIoN OF HOST TO PARASITIC ATTACK. 



Ar, mutilation of starch is described by R Hartig 1 in spruce- 

 nc.-dlcs attacked by L<ij>/i<>/t<'/'//ri/iiD macrosporum. In the pre- 

 sence of the fungus-mycelium, an increased production and 

 storage of starch takes place at a time when it is being only 

 -lo\vly funned in normal needles. If the needles become diseased 

 during May, a season when they are already full of starch, 

 this remains intact in the dead cells till October, when it begins 

 to be used up. 



Wakkcr observed accumulation of starch in comfrey with 

 A** ill i" in nx/ii/'ij'ii/ii, in buckthorn with Accidium rhamni, in 

 hawthorn with Jlnt^fdia />'rrata, in Sisymbrium officinale and 

 "[her plants with Ci/stopus, in roots of Brassica inhabited by 

 Plasmodiophora brassicae, and in hypertrophied scales of alder 

 catkins with JK.'vascus. Many other examples are given through- 

 out the literature of plant-pathology. 



Particularly noteworthy is a case of starch preservation in 

 oak -wood destroyed by Polyporus dryadcus and P. iyniarius 



simultaneously. 2 In the wood infested by 

 either of the fungi alone the starch is dis- 

 solved, but at the boundary where the two 

 meet it remains in the medullary rays ; 

 these, in consequence, appear snowy white, 

 and consist almost exclusively of unchanged 

 starch-grains, while the liguih'ed cell-walls 

 have been converted into cellulose or corn- 

 s'. ''Wfyr lately absorbed (Fig. 10). Loew 3 remarks in 

 regard to this : " One must assume here a 



* -4 , I . . , : .> . k 'it *i*A M l i" ' . t 



variation in the kinds of diastase, and a 

 neutralizing effect of the one on the other, 

 in somewhat the same manner as pepsin acts 

 on tyrosin. One is also reminded of two 

 optical antipodes which easily unite into an 

 optically neutral body " (e.g. sugar isomers). 



The dissolution of starch by fungi has 

 been examined in detail by Hartig. The 

 wood-destroying fungi dissolve the reserve 



starch-grains laid up in the wood-parenchyma in various ways. 



Assuming the view of Naegeli, that starch-grains consist of a 



\\'i,-hti<je Krankheiten d. Waldbciumen, 1874. 

 -R. Hartig, Zersetzung$ersc!ieinu>t</en, 1878. 

 : 'Loe\v, 0., Ein naturlichts System d. Gift-Wirkunyen. Munich, 1893. 



' 



\ 



' 



'. i . i 



". The cells are 

 still full of undissolved 

 starch, hence appear white. 

 (v. Tubeuf phot ) 



