#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w, x = 0;
  string a[55];
  cin >> h >> w;
  for (int i = 0; i < h; i++) cin >> a[i];
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (a[i][j] == '#') {
        if (i != 0) {
          if (a[i - 1][j] == '#') continue;
        }
        if (i != h - 1) {
          if (a[i + 1][j] == '#') continue;
        }
        if (j != 0) {
          if (a[i][j - 1] == '#') continue;
        }
        if (j != w - 1) {
          if (a[i][j + 1] == '#') continue;
        }
        cout << "no" << endl;
        return 0;
      }
    }
  }
  cout << "yes" << endl;
  return 0;
}
