#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  cin >> h >> w;
  bool a[h][w], ans = true;
  char s;
  for (int i = 0; i < h; i++)
    for (int j = 0; j <= w; j++) {
      scanf("%c", &s);
      switch (s) {
        case '#':
          a[i][j] = true;
          break;
        default:
          a[i][j] = false;
          break;
      }
    }
  for (int i = 0; i < h; i++)
    for (int j = 0; j <= w; j++) {
      if (a[i][j] == true)
        if (a[i - 1][j] == false && a[i][j - 1] == false)
          if (a[i + 1][j] == false && a[i][j + 1] == false) ans = false;
    }
  if (ans == true)
    cout << "yes";
  else
    cout << "no";
}
