GLS, as.formula and subsitute

Dear all,

I am trying to feed a formula object into GLS using substitute() and as.formula(). What am I doing
wrong here?

##
models <- function(resp=quote(resp),DF=quote(DF)) {
f1=substitute(resp~Time,list(resp=quote(resp)))
gls(as.formula(f1),data=DF)
}

models(resp="follicles","Ovary")

##
Many thanks for your help!

Best wishes
Christoph

PD Dr Christoph Scherber
Georg-August University Goettingen
Department of Crop Science
Agroecology
Grisebachstrasse 6
D-37077 Goettingen
Germany
phone 0049 (0)551 39 8807
fax 0049 (0)551 39 8806
http://www.gwdg.de/~cscherb1