#include <bits/stdc++.h>
using namespace std;
string s[60];
bool black[60][60];
bool ans = true;
int main() {
  int n, k;
  cin >> n >> k;
  for (int i = 0; i < n; i++) {
    cin >> s[i];
    for (int j = 0; j < k; j++) {
      if (s[i][j] == '.')
        black[i][j] = false;
      else
        black[i][j] = true;
    }
  }
  for (int i = 0; i < n; i++)
    for (int j = 0; j < k; j++) {
      int cnt = 0;
      if (black[i + 1][j] == 0 && i + 1 < n && j < k) cnt++;
      if (black[i][j + 1] == 0 && i < n && j + 1 < k) cnt++;
      if (black[i - 1][j] == 0 && i >= 0 && j - 1 >= 0) cnt++;
      if (black[i][j - 1] == 0 && i - 1 >= 0 && j >= 0) cnt++;
      if (cnt == 4) ans = false;
    }
  if (ans)
    cout << "Yes";
  else
    cout << "No";
  system("pause");
  return 0;
}
