#include <bits/stdc++.h>
using namespace std;
bool dfs(int, int);
int dx[4] = {-1, 0, 1, 0};
int dy[4] = {0, -1, 0, 1};
char s[50][50];
int h, w;
int main() {
  bool flag = true;
  cin >> h >> w;
  int d = 0;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      cin >> s[i][j];
      if (s[i][j] != '.') d++;
    }
  }
  if (d == 0)
    cout << "Yes" << endl;
  else {
    for (int i = 0; i < h; i++) {
      for (int j = 0; j < w; j++) {
        if (!dfs(i, j)) {
          flag = false;
          break;
        }
      }
      if (!flag) break;
    }
    if (!flag)
      cout << "No" << endl;
    else
      cout << "Yes" << endl;
  }
}
bool dfs(int y, int x) {
  int c = 0;
  for (int i = 0; i < 4; i++) {
    int ny = y + dy[i];
    int nx = x + dx[i];
    if (nx < 0 || ny < 0 || nx > w || ny > h) continue;
    if (s[y][x] == '.') continue;
    if (s[y][x] == '#') {
      if (s[ny][nx] == s[y][x]) {
        c++;
      }
    }
  }
  if (c == 0) return false;
  return true;
}
