#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W;
  cin >> H >> W;
  char s[H + 2][W + 2];
  for (int i = 1; i <= H; i++) {
    for (int j = 1; j <= W; j++) {
      cin >> s[i][j];
    }
  }
  for (int i = 0; i < H + 2; i++) {
    s[i][0] = 0;
    s[i][H + 1] = 0;
  }
  for (int i = 0; i < W + 2; i++) {
    s[0][i] = 0;
    s[W + 1][i] = 0;
  }
  bool flag = 0;
  for (int i = 1; i <= H; i++) {
    for (int j = 1; j <= W; j++) {
      if (s[i][j] != s[i - 1][j] && s[i][j] != s[i][j - 1] &&
          s[i][j] != s[i + 1][j] && s[i][j] != s[i][j + 1] && s[i][j] == '#') {
        flag = 1;
      }
    }
  }
  if (flag) {
    cout << "No" << endl;
    return 0;
  }
  cout << "Yes" << endl;
  return 0;
}
