Fit lines in intxplot

Dear R help,

I tried to add linear fit lines in intxplot by adding "index.cond = function(x,y) coef(lm(y ~ x))[1]" inside the intxplot().? It didn't help.? I would appreciate any help.
My dataset and codes are pasted below.

Thanks,
A.K.


datGreen<- read.table(text="
Time,? ? DarkSt,? ? LightSt
0,? ? 0,? ? 1
1,? ? 0.03,? ? 0.82
2,? ? 0.06,? ? 0.91
3,? ? 0.12,? ? 0.64
4,? ? 0.12,? ? 0.73
5,? ? 0.12,? ? 0.64
6,? ? 0.09,? ? 0.64
7,? ? 0.09,? ? 0.64
8,? ? 0.09,? ? 0.64
9,? ? 0.09,? ? 0.64
10,? ? 0.12,? ? 0.64
11,? ? 0.09,? ? 0.64
12,? ? 0.09,? ? 0.73
13,? ? 0.06,? ? 0.73
14,? ? 0.06,? ? 0.64
15,? ? 0.09,? ? 0.73
16,? ? 0.09,? ? 0.73
17,? ? 0.09,? ? 0.73
18,? ? 0.12,? ? 0.64
19,? ? 0.09,? ? 0.64
20,? ? 0.12,? ? 0.64
",sep=",",header=TRUE)

dat1<-data.frame(time=rep(c(1:20),rep(2,20)),trt=rep(c('D','L'),each=1))
? ? ? datG<-data.frame(matrix(rbind(datGreen$DarkSt,datGreen$LightSt),ncol=1,byrow=TRUE))
? ? ? colnames(datG)<-"Response"
? ? ? dat2G<-datG[-1,]
? ? ? dat2G<-data.frame(dat2G)
? ? ? dat2G<-dat2G[-1,]
? ? ? dat2G<-data.frame(dat2G)
? ? ? colnames(dat2G)<- "Response"
? ? ? dat3G<-data.frame(dat1,dat2G)
? ? ? dat4G<-transform(dat3G,trt=ordered(trt,levels=c('D','L')))
? ? ?  dat4G$time<-factor(dat4G$time)
? ? ? position(dat4G$time)<-as.numeric(levels(dat4G$time))
? ? ? position(dat4G$trt)<-c(10,20)
#pdf("GreenDarkvsLight.pdf")
intxplot(Response~time,data=dat4G,groups=trt,se=TRUE,ylim=c(0,1),main="Response in Green light")

#dev.off()

I expect to get fit lined as in the xyplot:
xyplot(Response ~ time, dat4G,
? ? ? ? ? ? ? ? type = c( "g", "p","r"), groups=trt, index.cond = function(x,y) coef(lm(y ~ x))[1],
? ? ? ? ? ? ?  xlab = "Time in min",
? ? ? ? ? ? ?  ylab = "Response", main="Response in Green light")