#include <bits/stdc++.h>
using namespace std;
const int N = 55;
const int dir[4][2] = {0, 1, 1, 0, 0, -1, -1, 0};
char a[N][N];
int cnt;
int n, m;
bool vis[N][N];
void dfs(int x, int y) {
  cnt++;
  for (int i = 0; i < 4; i++) {
    int nx = x + dir[i][0];
    int ny = y + dir[i][1];
    if (nx >= 0 && nx < n && ny >= 0 && ny < m && a[nx][ny] == '#' &&
        !vis[nx][ny]) {
      vis[nx][ny] = 1;
      dfs(nx, ny);
      vis[nx][ny] = 0;
    }
  }
}
int main() {
  while (cin >> n >> m) {
    getchar();
    for (int i = 0; i < n; i++) {
      cin >> a[i];
    }
    bool flag = 0;
    for (int i = 0; i < n; i++) {
      for (int j = 0; j < m; j++) {
        if (a[i][j] == '#') {
          cnt = 0;
          dfs(i, j);
          if (cnt == 1) {
            flag = 1;
            cout << "No" << endl;
            break;
          }
        }
      }
      if (flag) break;
    }
    if (!flag) cout << "Yes" << endl;
  }
  return 0;
}
