#include <bits/stdc++.h>
using namespace std;
int H, W;
char grid[55][55];
string ans;
int main() {
  cin >> H >> W;
  ans = "Yes";
  for (int i = 1; i <= H; ++i) {
    for (int j = 1; j <= W; ++j) {
      cin >> grid[i][j];
    }
  }
  for (int i = 1; i <= H; ++i) {
    for (int j = 1; j <= W; ++j) {
      char tmp;
      if (grid[i][j] == '.') {
        tmp = '#';
      } else {
        tmp = '.';
      }
      if (grid[i - 1][j] == tmp && grid[i][j - 1] == tmp &&
          grid[i + 1][j] == tmp && grid[i][j + 1] == tmp) {
        ans = "No";
      }
    }
  }
  cout << ans << endl;
  return 0;
}
