34 REACTION OF HOST TO PAEASITIC ATTACK. 



Accumulation of starch is described by E. Hartig^ in spruce- 

 needles attacked by Loplwdermium, 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 

 slowly formed 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. 



Wakker observed accumulation of starch in comfrey with 

 Aecidium asperifolii, in buckthorn with Aeeidium rhamni, in 

 hawthorn with Roestdia laceraia, in Sisymbrium officinale and 

 other plants with Cystopus, in roots of Brassica inhabited by 

 Plasmodiophora brassicae, and in hypertrophied scales of alder 

 catkins with Uxoascus. 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 Polypoms dryadeus and P. igniarius 

 simultaneously.^ 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 Ugnified cell-walls 

 have been converted into cellulose or com- 

 pletely absorbed (Fig. 10). Loew' remarks in 

 regard to this : " One must assume here a 

 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 

 ■of^o'ak-wMd'deSroyed^bl Optically ucutral body" {e.g. sugar isomers). 

 ftiif^fuir'of^undSoiTCd The dissolution of starch by fungi has 

 ''"TubeuTrhofr""""" 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 



' Wichtige Kranhheiten d. WcUdbdumen, 1874. 



'R. Hartig, Zersetzuiigserscheinungen, 1878. 



^Loew, 0., Ein naturliches System d. Oift-Wirkungen. Munich, 1893. 



