EFFECT OF PARASITIC FUNGI ON CELL-CONTENTS. 



35 



cellulose and a granulose part, Hartig describes the process thus 

 {Fig. 11). The mycelium of species like Polyporus igniarius 

 gives oft' some ferment which dissolves the starch-grains, by cor- 

 roding them from the outside inwards, so as to form holes and 

 canals similar to those in 

 starch-grains in process of 

 dissolution in the cells of a 

 sprouting potato. In others, 

 e.g. Thelephora perdix, the 

 granulose is first dissolved 

 from without inwards, so that 

 finally only the starch-cellulose 



remains, occupying a region no. n.-Stareh grams from the oak, m pro- 



towardt! thp mitpr i-iarfa nf cess of dissolution by ferments, a, of r/i€fcj7/iora 



UUWdlUb tne OUrer pares OI perdU ; b, ot Polj/pm-us sutphureus ; c, ol Pol)- 



t"hp arnin n« a Iritirl <-if Vinot porus isniarius. in a and ii the iodine-reaction 



Liie gram as a Kina oi nusK, r^ ^^^^^ ^,y s^^jng. (After r. Hartig.) 

 which is in time gradually 



used up. In Polyporus sulphuretis the operation is reversed ; 

 the starch-cellulose appears to be dissolved out first, leaving 

 a residue of granulose. These observations were based on 

 the assumption that the starch-grain consisted of a granu- 

 lose portion which turned blue with iodine, and a starch- 

 cellulose portion which became yellow ; or again, on treating 

 the starch-grains with dilute acids the granulose was dissolved, 

 while the cellulose remained in the form of a skeleton. 

 Although more recent investigations have shown that the 

 cellulose-skeleton results from the action of the acids, and that 

 this view of the constitution of the starch-grain was not quite 

 correct, yet Hartig's observations prove that the various fungus- 

 ferrnents have each their own action on starch-grains ; his 

 results are also supported by other facts. 



Other fungi besides Polyporeae utilize the starch of their 

 host-plants, thus Phytophthora in leaves of the potato. 



The formation of calcium oxalate is influenced by action of 

 parasites. From Wakker's synopsis of the phenomena of hyper- 

 trophy, we find that calcium oxalate normally present in crystal- 

 sacs in leaves and flowers of Phamnus Frangula, is wanting in 

 parts deformed by Aecidium rhamni ; crystal-sacs are less 

 abundant in diseased stems than in healthy ; the calcium oxalate 

 in galls of Exdbasidium is not present in crystal-sacs, as in the 

 non-deformed organs, but as ill-defined solitary crystals of limited 



