#include <bits/stdc++.h>
int main() {
  int h, w, i, j, flag = 1;
  char a[51][51] = {'0'};
  scanf("%d %d", &h, &w);
  for (i = 0; i < h; i++) {
    scanf("%s", a[i]);
  }
  for (i = 0; i < h; i++) {
    for (j = 0; j < w; j++) {
      if (a[i][j] == '.') {
        if ((i == 0 || a[i - 1][j] != '.') && (j == 0 || a[i][j - 1] != '.') &&
            (a[i + 1][j] != '.') && (a[i][j + 1] != '.'))
          flag = 0;
      }
    }
  }
  if (flag)
    printf("Yes");
  else
    printf("No");
}
