#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
const int INF = 0x3f3f3f3f;
const long long INFL = 0x3f3f3f3f3f3f3f3f;
int h, w;
char field[55][55];
bool checked[55][55];
int dfs(int x, int y) {
  if (x < 0 || w <= x || y < 0 || h <= y || field[x][y] == '.') return 0;
  if (checked[x][y]) return 0;
  checked[x][y] = true;
  field[x][y] = '.';
  return 1 + dfs(x + 1, y) + dfs(x - 1, y) + dfs(x, y + 1) + dfs(x, y - 1);
}
int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  cin >> h >> w;
  for (long long i = 0; i < (h); i++) {
    for (long long j = 0; j < (w); j++) {
      cin >> field[i][j];
    }
  }
  for (long long i = 0; i < (h); i++) {
    for (long long j = 0; j < (w); j++) {
      if (field[i][j] == '#') {
        if (dfs(i, j) <= 1) {
          cout << "No" << endl;
          return 0;
        }
      }
    }
  }
  cout << "Yes" << endl;
  return 0;
}
