V,W = map(int,input().split())
canvas = []
for i in range(V):
  canvas.append(list(map(str,input())))

  
def line():
  for i in range(V):
    for s in range(W-1):
      if canvas[i][s]=="#" and canvas[i][s+1]=="#":
        return True
        break
      break
  
              
def row():
  for i in range(V-1):
    for s in range(W):
      if canvas[s][i]=="#" and canvas[s][i+1]=="#":
        return True
        break
      break
     
        
line = line()
row = row()
if line != True and row != True:
  print("No")
else:
  print("Yes")