#include <bits/stdc++.h>
using namespace std;
void solve(vector<vector<char>>& maps, int x, int y, int h, int w, int& count) {
  count++;
  maps[y][x] = '.';
  if (x > 0) {
    if (maps[y][x - 1] == '#') solve(maps, x - 1, y, w, h, count);
  }
  if (x < w - 1) {
    if (maps[y][x + 1] == '#') solve(maps, x + 1, y, w, h, count);
  }
  if (y > 0 && maps[y - 1][x] == '#') solve(maps, x, y - 1, w, h, count);
  if (y < h - 1 && maps[y + 1][x] == '#') solve(maps, x, y + 1, w, h, count);
  return;
}
int main(void) {
  int h, w;
  cin >> h >> w;
  vector<vector<char>> maps;
  for (int i = 0; i < h; i++) {
    vector<char> map;
    for (int j = 0; j < w; j++) {
      char temp;
      cin >> temp;
      map.push_back(temp);
    }
    maps.push_back(map);
  }
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      int count = 0;
      if (maps[i][j] == '#') solve(maps, j, i, h, w, count);
      if (count == 1) {
        cout << "No" << endl;
        return 0;
      }
    }
  }
  cout << "Yes" << endl;
  return 0;
}
