#include <bits/stdc++.h>
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, -1, 0, 1};
using namespace std;
char s[51][51] = {};
int h, w;
int bfs(int y, int x) {
  int size = 0;
  queue<pair<int, int>> que;
  que.push(make_pair(y, x));
  while (!que.empty()) {
    pair<int, int> now = que.front();
    que.pop();
    int nowx, nowy;
    nowy = now.first;
    nowx = now.second;
    s[nowy][nowx] = '.';
    size++;
    for (int i = 0; i < 4; i++) {
      int nexty = nowy + dy[i];
      int nextx = nowx + dx[i];
      if (nextx < 0 or nexty < 0 or nexty >= h or nextx >= w or
          s[nexty][nextx] == '.') {
        continue;
      } else {
        que.push(make_pair(nexty, nextx));
      }
    }
  }
  return size;
}
int main(void) {
  cin >> h >> w;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      cin >> s[i][j];
    }
  }
  bool ok = true;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (s[i][j] == '#') {
        if (bfs(i, j) <= 1) {
          ok = false;
          cout << "No" << endl;
          return 0;
        }
      }
    }
  }
  cout << "Yes" << endl;
  return 0;
}
