#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w, i, j;
  cin >> h >> w;
  char s[h + 1][w + 1];
  for (i = 1; i <= h; i = i + 1) {
    for (j = 1; j <= w; j = j + 1) {
      cin >> s[i][j];
    }
  }
  for (i = 1; i <= h; i = i + 1) {
    for (j = 1; j <= w; j = j + 1) {
      if (s[i][j] == '#') {
        if (s[i][j + 1] == '#' || s[i + 1][j] == '#' || s[i][j - 1] == '#' ||
            s[i - 1][j] == '#')
          i = i;
        else {
          cout << "N0" << endl;
          return 0;
        }
      }
    }
  }
  cout << "Yes" << endl;
  return 0;
}
