130 DIE-BACK OF CHILLIES IN BIHAR 
when it reaches a fork the infection runs upthe sound limb. Jn some cases 
the attack starts not from the growing point but from a wound on the stem. 
As the disease progresses, the infected part of the stem takes on an enamelled 
white colour and is sharply demarcated from the healthy green bark by a black 
line running round the whitened area. The white of the diseased part is 
punctuated by scattered black bristly and minute elevations, which are the 
acervuli of the fungus (Plate I, fig. 1). 
(b) The fruit. The fruits become visibly diseased when they turn red, 
very seldom while they are still green. The first outward sign of infection is 
the appearance of a smail black circular speck, generally sharply defined but 
at times diffused. The disease spreads not concentrically, but more in the 
direction of the long axis of the pod, so that the originally circular spot becomes 
more or less elliptical. As the infection progresses the spot is either diffused 
and black er greenisk-black or dirty grey, or 1s markedly delimited by a thick 
and sharp black outline enclosing a lighter black or straw-coloured area. 
Two or more diseased spots may hecome confluent, thereby destroying the 
regularity of the individual spots, but the delimiting black line is not always 
completely obliterated where the infected areas have united. Badly diseased 
pods lose their normal red colour and turn straw-coloured or in some cases 
pale white (Plate I, fig. 3). The acervuli are generally densely gregarious or 
scattered all over the infected parts ; at times they are concentric. They 
project a little above the surface of the pod and are bristly and carbonaceous. 
The spores ooze out of the acervuli in pink masses or strings under moist 
conditions, 
When a diseased pod is cut open the lower surface of the skin is found 
covered with minute, black, spherical elevations ; these are the stromatic 
masses or sclerotia of the fungus. In advanced cases the seeds are covered by 
a felt of white mycelium, in which are embedded a few black or grey-green 
stromatic hodies. Infected seeds turn rusty in colour. 
Microscopie characters. 
(a) The stem. Sections through a slightly diseased stem show the infected 
tissues to have turned yellow or brown and the cell cavities to be filled with a 
smilarly coloured gummy substance which hides the hyphe. The use of 
clearing agents helps in disclosing them. The tissues outside the xylem are 
more readily discoloured and destroyed than the xylem itself. Diseased xylem 
tissues get. discoloured, but not so much as the soft outer tissues ; and the 
presence of the hyphe within the vessels can be clearly traced. Even in very 
advanced cases of attack, the xylem vessels have not heen found choked 
