#include <bits/stdc++.h>
using namespace std;
int dfs(int, int, int, int, int);
char field[50][50 + 1];
int main() {
  int H, W, cnt = 0;
  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] == '#') {
        int size = dfs(i, j, 1, H, W);
        if (size < 2) {
          cout << "No" << endl;
          return 0;
        }
      }
    }
  }
  cout << "Yes" << endl;
  return 0;
}
int dfs(int y, int x, int size, int H, int W) {
  field[y][x] = '.';
  int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
  for (int i = 0; i < 4; i++) {
    int nx = x + dx[i], ny = y + dy[i];
    if (0 <= ny && ny < H && 0 <= nx && nx < W) {
      if (field[ny][nx] == '#') {
        size = dfs(ny, nx, ++size, H, W);
        break;
      }
    }
  }
  return size;
}
