#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  int k;
  cin >> h >> w;
  vector<string> matric(h);
  string str;
  vector<vector<bool> > rst(h, vector<bool>(w, false));
  for (int i = 0; i < h; i++) {
    cin >> str;
    matric[i] = str;
  }
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (i < h - 1 && matric[i][j] == matric[i + 1][j]) {
        rst[i][j] = true;
        rst[i + 1][j] = true;
      }
      if (j < w - 1 && matric[i][j] == matric[i][j + 1]) {
        rst[i][j] == true;
        rst[i][j + 1] == true;
      }
    }
  }
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (matric[i][j] == '#' && rst[i][j] == false) cout << "No" << endl;
      return 0;
    }
  }
  cout << "Yes" << endl;
  return 0;
}
