#include <bits/stdc++.h>
int main(void) {
  int i, j, h, w, p;
  char s[50][50];
  scanf("%d", &h);
  scanf("%d", &w);
  p = 0;
  for (i = 1; i <= h; i++) {
    for (j = 1; j <= w; j++) {
      scanf("%c", &s[i - 1][j - 1]);
    }
  }
  for (i = 0; i <= h - 1; i++) {
    for (j = 0; j <= w - 1; j++) {
      if (s[i][j] == s[i - 1][j] || s[i][j] == s[i][j - 1] ||
          s[i][j] == s[i + 1][j] || s[i][j] == s[i][j + 1]) {
      } else if (s[i][j] == '#') {
        p = 1;
        break;
      }
    }
  }
  if (p == 0) {
    printf("Yes");
  } else {
    printf("No");
  }
  return 0;
}
