#include <bits/stdc++.h>
using namespace std;
int N, M;
char s[55][55];
int dfs(int x, int y) {
  int r = 1;
  s[x][y] = 0;
  if (s[x + 1][y] == '#') r += dfs(x + 1, y);
  if (s[x][y + 1] == '#') r += dfs(x, y + 1);
  if (s[x - 1][y] == '#') r += dfs(x - 1, y);
  if (s[x][y - 1] == '#') r += dfs(x, y - 1);
  return r;
}
int main() {
  scanf("%d%d", &N, &M);
  for (int i = 0; i < N; i++) {
    scanf("%s", s[i + 1] + 1);
  }
  for (int i = 1; i <= N; i++) {
    for (int j = 1; j <= M; j++) {
      if (s[i][j] == '#') {
        if (dfs(i, j) < 2) {
          cout << "No\n";
          return 0;
        }
      }
    }
  }
  cout << "Yes\n";
  return 0;
}
