h, w = map(int, input().split())
L = ['.'*(w+1)]
for i in range(h):
  L.append('.'+input()+'.')
L.append('.'*(w+1))  

out = 1
for i in range(1, h+1):
  for j in range(i+1, h+1):
    if L[i][j] == '#':
      if L[i][j+1] == '#' or L[i][j-1] == '#' or L[i-1][j] == '#' or L[i+1][j] == '#':
        out *= 1
      else:
        out *= 0

if out == 1:
  print('Yes')
else:
  print('No')