#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  cin >> h >> w;
  int grid[w][h];
  for (int y = 0; y < h; y++) {
    for (int x = 0; x < w; x++) {
      char s;
      cin >> s;
      grid[x][y] = s == '#' ? 1 : 0;
    }
  }
  bool canDraw = true;
  for (int x = 0; x < w; x++) {
    for (int y = 0; y < h; y++) {
      int top = grid[x][y - 1];
      int left = grid[x - 1][y];
      int right = grid[x + 1][y];
      int bottom = grid[x][y + 1];
      int center = grid[x][y];
      bool roundWhite = top + left + right + bottom == 0;
      if (roundWhite && center == 1) {
        canDraw = false;
      }
    }
  }
  string ans = canDraw ? "yes" : "no";
  cout << ans << endl;
  return 0;
}
