#include <bits/stdc++.h>
using namespace std;
int h, w, sz[5005];
char s[52][52];
bool used[52][52];
int cnt = 0;
void dfs(int x, int y) {
  used[x][y] = true;
  if (x > 1 && !used[x - 1][y] && s[x - 1][y] == '#') {
    sz[cnt]++;
    dfs(x - 1, y);
  }
  if (x < h && !used[x + 1][y] && s[x + 1][y] == '#') {
    sz[cnt]++;
    dfs(x + 1, y);
  }
  if (y > 1 && !used[x][y - 1] && s[x][y - 1] == '#') {
    sz[cnt]++;
    dfs(x, y - 1);
  }
  if (y < w && !used[x][y + 1] && s[x][y + 1] == '#') {
    sz[cnt]++;
    dfs(x, y + 1);
  } else
    return;
}
int main() {
  ios::sync_with_stdio(false);
  cin >> h >> w;
  bool check = false;
  for (int i = 1; i <= h; i++)
    for (int j = 1; j <= w; j++) cin >> s[i][j];
  for (int i = 1; i <= h; i++)
    for (int j = 1; j <= w; j++)
      if (!used[i][j] && s[i][j] == '#') {
        sz[++cnt] = 1;
        dfs(i, j);
      }
  if (cnt == 0) {
    cout << "No" << endl;
    return 0;
  }
  for (int i = 1; i <= cnt; i++)
    if (sz[cnt] == 1) {
      check = true;
      break;
    }
  if (check)
    cout << "No" << endl;
  else
    cout << "Yes" << endl;
  return 0;
}
