EFFECT OF PARASITIC Ft/Mil ( >N CELL CONTENTS. 33 



parts, which become pale and die. This is exemplified in 

 tin HI asdepiadewm on the leaves of Vincetoxium, '//////- 



clavctri>"'fi '///!> on the quince, Um-in/iln aceris mi 

 the Xorway maple, llhi/tixiim i>nnrtntn>a on Af> r *ji/<'f/>/n. 



Intermediate between these two extremes are cases when- 

 the chlorophyll is retained, but in much reduced quantity. !'- -i 

 example, organs under the influence of .!/<./< >.*//.> ,///// incancu or 

 A'l-'nI'm HI I'liitiiu'irt, though still green, are pale in contrast to 

 those normally deep green; leaves attacked by Teronosporeae, -.-/. 

 (_''<r;i<l<ili* or A'lU'iiiinii- with rittx-iiKijxjrii />////"""'", and Am limn, 

 with Acciditnn p>//n-fiif///,i or Purrin'm fnxni ; leaves of Cir^unu 

 containing mycelium of 7V<r/,//" \////cco//'//.s ; leaves of alder 

 with E.>-n<ix<-iis <y;/y/////////.s-, and many 'others. This paler coloura- 

 tion of diseased plants is frequently an easy means of recognizing 

 them amongst the healthy ones. 



The third case is that of " mycetogenous chloranthy " or the 

 development of green colour in organs normally of some other 

 i-nloiir. Wakker has jmived this in the petals and stamens of 

 Brassica tii;/m and ,v/.s///// /,//'///// pannonicum attacked by ^//x/^//s 

 ami /'I'l-n/tnxjim-'i. Likewise Magnus showed its existence in 

 flowers of A/f nnni' ,-<iiinii<'ii]ni,li* with 



The cell-sap, in some cases of hypertrophy, a>sume.> mi the 

 sunny side a rose colour; thus in galls caused by /,'</" 's /</</'/// 

 on alpine-rose and cowberry, pear-leaves with J!n, .</,/ in <-nn<;llnt<i 

 and Pclystigma ntbru/m, catkins of alder attacked by A''n//sc//>, 

 and galls caused by Tn^li i-'nm earned in the s\\eet birch. Tin- 

 epidermal galls, due to some species of N/////7/////-////// (X rnl>i-<>- 

 cinctum, X <',/--i/iii<'s, etc.), exhibit an intmsr carmine cnlmi, 

 \'t-llow coloration occurs, accni'din.u to \\'akker, in nettle, buck- 

 thorn, and many plants when t'rci|Ucnted by I'lvdinrae. Ther. 

 may also be a yellow colour due to tin- yellow oily content- 

 of the mycelium shining through tin- host-tissues, as in spruce- 



needles with f '// rt/^n/i // lit nhntis. 



lii CMii-nlcrin- the elt'cci ( .r parasitic f'un^i on the starch- 

 COntentfl of the host-jilant, two very distiml cases may be 

 observi-d. There may be, for a time, a greater accumulation 

 of starch in tin- attacked parts than in the normal, or the 

 may ili>-i.l\i- any -larch present and utili/c it at ODC6 



i 



