#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W;
  bool canpaint = true;
  cin >> H >> W;
  string input[50];
  for (int i = 0; i < H; i++) {
    cin >> input[i];
  }
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      if (input[i][j] == '#') {
        if (input[i - 1][j] == '#')
          ;
        else if (input[i + 1][j] == '#')
          ;
        else if (input[i][j - 1] == '#')
          ;
        else if (input[i][j + 1] == '#')
          ;
        else
          canpaint = false;
      }
    }
  }
  if (canpaint) {
    cout << "yes";
  } else {
    cout << "no";
  }
  return 0;
}
