row = list(map(int, input().split()))
s = [input().split() for i in range(row[0])]
for i in range(row[0]):
    s[i] = list(s[i][0])
dx = [0, -1, 1, 0]
dy = [-1, 0, 0, 1]
for i in range(row[0]):
    for j in range(row[1]):
        if s[i][j] == "#":
            Flag = False
            for d in range(4):
                nx = i + dx[d]
                ny = j + dy[d]
                if 0 <= nx < row[0] and 0<= ny < row[1]:
                    if s[nx][ny] == "#":
                        Flag = True
                        break
            if Flag != True:
                break
    if Flag != True:
        print("No")
        break
if Flag:
    print("Yes")

