def solve():
    H,W = list(map(int, input().split()))
    S = ['.'*(W+2)]+['.'+input()+'.' for _ in range(H)]+['.'*(W+2)]
    result = 'yes'
    
    # print(S)
    
    for i in range(1,H+1):
        for j in range(1,W+1):
            if S[i][j] == '#':
                if not(S[i+1][j] == '#' or S[i-1][j] == '#' or S[i][j+1] == '#' or S[i][j-1] == '#'):
                    result = 'no'
                    break
    
    print( result )
    
solve()