#include <bits/stdc++.h>
using namespace std;
int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, 1, 0, -1};
int H, W;
bool ok = false;
const int max_n = 100;
char s[max_n][max_n];
void dfs(int x, int y, int cnt) {
  s[x][y] = '.';
  for (int i = 0; i < 4; i++) {
    int nx = x + dx[i], ny = y + dy[i];
    if (nx >= 0 && ny >= 0 && nx <= H && ny <= W && s[nx][ny] == '#') {
      if (cnt == 0) {
        ok = true;
      }
      dfs(nx, ny, cnt + 1);
    }
  }
}
void solve() {
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      if (s[i][j] == '#') {
        dfs(i, j, 0);
        if (!ok) {
          cout << "No" << endl;
          return;
        }
      }
    }
  }
  cout << "Yes" << endl;
}
int main() {
  cin >> H >> W;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      cin >> s[i][j];
    }
  }
  solve();
  return 0;
}
