H,W = list(map(int,input().split()))
table = []
for i in range(H):
    table.append(list(input()))
if table == [["#"]]:
    print("No")
    exit()
for i in range(H):
    for j in range(W):
        A = table[i][j]
        if A == "#":
            try:
                if table[i-1][j] == "#":
                    break
            except IndexError:
                pass
            try:
                if table[i+1][j] == "#":
                    break
            except IndexError:
                pass
            try:
                if table[i][j-1] == "#":
                    break
            except IndexError:
                pass
            try:
                if table[i][j+1] == "#":
                    break
            except IndexError:
                pass
            print("No")
            exit()
        else:
            continue
print("Yes")