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

line = []
for i in range(V):
  for s in range(W-1):
    if canvas[i][s]=="#" and canvas[i][s+1]=="#":
      line.append("OK")
    else:
      line.append("NO")
        
row = []        

for i in range(V-1):
  for s in range(W):
    if canvas[s][i]=="#" and canvas[s][i+1]=="#":
      row.append("OK")
    else:
      row.append("NO")
      
if "OK" not in line and "OK" not in row:
  print("No")
else:
  print("Yes")