#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W;
  char S[50][50];
  char tmp;
  cin >> H >> W;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      cin >> tmp;
      S[i][j] = tmp;
    }
  }
  bool flag = false;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      if (S[i][j] == '#') {
        if (S[i][j] == S[i - 1][j] || S[i][j] == S[i + 1][j] ||
            S[i][j] == S[i][j - 1] || S[i][j] == S[i][j + 1]) {
          flag = true;
        } else {
          flag = false;
        }
      }
    }
  }
  if (flag) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }
  return 0;
}
