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