#include <bits/stdc++.h>
using namespace std;
int h, w;
char grid[50][50];
int main() {
  cin >> h >> w;
  for (int i = 0; i < h; i++)
    for (int j = 0; j < w; j++) cin >> grid[i][j];
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      bool ans = false;
      if (grid[i][j] == '#') {
        int x = 1;
        int y = 0;
        for (int k = 0; k < 4; k++) {
          if (j + x >= 0 && j + x < w && i + y >= 0 && i + y < h) {
            if (grid[i + y][j + x] == '#') {
              cout << "ngoniki" << endl;
              ans = true;
            }
          }
          int prex = x;
          x = y;
          y = -prex;
        }
        if (!ans) {
          cout << "No" << endl;
          return 0;
        }
      }
    }
  }
  cout << "Yes" << endl;
  return 0;
}
