#include <bits/stdc++.h>
using namespace std;
int BOARD[50][50];
int main() {
  int h, w, flag = 0;
  string s;
  cin >> h >> w;
  for (int i = 0; i < h; i++) {
    cin >> s;
    for (int j = 0; j < w; j++) {
      if (s[j] == '.') {
        BOARD[i][j] = 0;
      } else {
        BOARD[i][j] = 1;
      }
    }
  }
  for (int i = 1; i < h - 1; i++) {
    for (int j = 0; j < w; j++) {
      if (j == 0) {
        if (BOARD[i + 1][j] != BOARD[i][j] && BOARD[i - 1][j] != BOARD[i][j] &&
            BOARD[i][j + 1] != BOARD[i][j]) {
          flag = 1;
        }
      } else if (j == w - 1) {
        if (BOARD[i + 1][j] != BOARD[i][j] && BOARD[i - 1][j] != BOARD[i][j] &&
            BOARD[i][j - 1] != BOARD[i][j]) {
          flag = 1;
        }
      } else {
        if (BOARD[i + 1][j] != BOARD[i][j] && BOARD[i][j] != BOARD[i - 1][j] &&
            BOARD[i][j] != BOARD[i][j + 1] && BOARD[i][j] != BOARD[i][j - 1]) {
          flag = 1;
        }
      }
    }
  }
  if (flag == 0) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }
  return 0;
}
