h, w = map(int, input().split())
g = [input() for i in range(h)]

xi = [1,0,-1,0]
yi = [0,-1,0,1]
flag = True

for s in range(h):
    for t in range(w):
        if g[s][t] == '#':
            for u in range(4):
                if 0 <= s+xi[u] < h and 0 <= t+yi[u] < w and g[s+xi[u]][t+yi[u]] == '#':
                    break
            else:
                flag = False
                break
        else:
            continue
        break 
    if flag == False:
        break

                

if flag:
    print('Yes')
else:
    print('No')


