#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W;
  cin >> H >> W;
  char s[H][W];
  for (int i = 0; i < H; ++i) {
    for (int j = 0; j < W; ++j) {
      cin >> s[i][j];
    }
  }
  bool X = true;
  for (int i = 0; i < H; ++i) {
    for (int j = 0; j < W; ++j) {
      if (s[i][j] == '#') {
        if (s[i][j] == '.' && s[i][j] == '.' && s[i][j] == '.' &&
            s[i][j] == '.')
          X = false;
      }
    }
  }
  if (X)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
