How to store the file name in a single line??

hi,
i have a variable, in which i am storing the file names that are present in the current directory.

$ls -1
s1.txt
s2.txt
s3.txt

$FILES=`ls -ltr | grep "^-" | awk '{print $NF}'`
$echo $FILES
s1.txt
s2.txt
s3.txt

i want to store the files names in a single line in the variable FILES delimited by a space.
eg

$echo $FILES
s1.txt s2.txt s3.txt

is there a way??

Simply run ls without any options:

FILES="$( ls )"

OR

FILES="$( ls *.txt )"

ls will take directory also.. n there can be other type of files also..

FILES=$( ls -ltr | awk '/^-/{$0=$NF;ORS=FS;print}' )

or
FILES=$( ls -ltr | awk '/^-/{ORS=FS;print $NF}' )

FILES=$(find -name \*.txt -printf "%f ")
FILES=$(find -maxdepth 1 -type f -name \*.txt)

I recommend to store them like this - newline separated!
You have the option to convert to a space-separated list on the fly

set -f; echo $FILES
for file in FILES; do

thanks all of you for these many solutions..