#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
int H, W;
bool flag = true;
bool x[50][50];
bool y[50][50];
int main(void) {
  cin >> H >> W;
  for (int i = 0; i < H; i++) {
    for (int k = 0; k < W; k++) {
      char a;
      cin >> a;
      if (a == '#') x[i][k] = true;
      if (i != 0)
        if (x[i][k] == x[i - 1][k]) y[i][k] = y[i - 1][k] = true;
      if (i != H - 1)
        if (x[i][k] == x[i + 1][k]) y[i][k] = y[i + 1][k] = true;
      if (k != 0)
        if (x[i][k] == x[i][k - 1]) y[i][k] = y[i][k - 1] = true;
      if (k != W - 1)
        if (x[i][k] == x[i][k + 1]) y[i][k] = y[i][k + 1] = true;
    }
  }
  for (int i = 0; i < H; i++)
    for (int k = 0; k < W; k++) {
      if (x[i][k])
        if (!y[i][k]) {
          flag = false;
          break;
        }
      if (!flag) break;
    }
  if (flag)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
  return 0;
}
