#include <bits/stdc++.h>
using namespace std;
int H, W;
char M[51][51];
int main() {
  std::ios_base::sync_with_stdio(false);
  scanf("%d %d", &H, &W);
  for (int i = 0; i < H; i++) scanf("%s", M[i]);
  int ok = 1;
  if (H == 1 && W == 1 && M[0][0] == '.') ok = 0;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      if (M[i][j] == '.') continue;
      if ((i == 0 || M[i - 1][j] == '.') &&
          (i == H - 1 || M[i + 1][j] == '.') &&
          (j == 0 || M[i][j - 1] == '.') &&
          (j == W - 1 || M[i][j + 1] == '.')) {
        ok = 0;
        break;
      }
    }
    if (!ok) break;
  }
  if (ok)
    printf("yes\n");
  else
    printf("no\n");
  return 0;
}
