H, W = map(int, input().split(" "))

result = True
masu = [[0 for i in range(H+2)] for j in range(W+2)]
for h in range(1, H+1):
    s = "0"+input()+"0"
    masu[h] = list(s)

print(masu)    

for h in range(H+2):
    for w in range(W+2):
        if masu[h][w] == "#":
            if (masu[h][w] == masu[h+1][w]) or (masu[h][w] == masu[h][w+1]) or (masu[h][w] == masu[h-1][w]) or (masu[h][w] == masu[h][w-1]):
                pass
            else:
                result = False

if result:
    print("Yes")
else:
    print("No")