#include <bits/stdc++.h>
using namespace std;
int main() {
  int i, j, k, h, w;
  bool tf;
  char a[52][52];
  cin >> h >> w;
  memset(a, '.', sizeof(a));
  for (i = 1; i <= h; i++) {
    for (j = 1; j <= w; j++) cin >> a[i][j];
  }
  for (i = 1; i <= h; i++)
    for (j = 1; j <= w; j++) {
      if (a[i][j] == '#') {
        if (a[i + 1][j] == '#' || a[i - 1][j] == '#' || a[i][j - 1] == '#' ||
            a[i][j + 1] == '#')
          tf = true;
        else {
          tf = false;
          cout << "no";
          return 0;
        }
      }
    }
  cout << "yes";
}
