#include <bits/stdc++.h>
using namespace std;
char map[55][55];
int main() {
  int n, m;
  cin >> n >> m;
  for (int i = 1; i <= n; i++) scanf("%s", map[i] + 1);
  int flag = 1;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      if (map[i][j] == '#') {
        if (map[i - 1][j] == '#' || map[i][j - 1] == '#' ||
            map[i][j - 1] == '#' || map[i][j - 1] == '#')
          flag = 1;
        else
          flag = 0;
      }
    }
  }
  if (flag)
    cout << "Yes";
  else
    cout << "No";
  return 0;
}
