H,W  = map(int,input().split())
s = []
ans = 'Yes'
for _ in range(W):
    s.append(input())

for i in range(H-1):
    for j in range(W-1):
        if s[i][j]=='.':
            continue
        else:
            if s[i][j+1]=='.' and s[i+1][j]=='.':
                print('No')
                exit()
print(ans)