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

table = []

for i in range(H):
	table.append(list(input()))


def check(x,y):
	if x > 0:
		if table[y][x-1] == '.':
			print ('No')
			quit()
			
	if x >= W:
		if table[y][x+1] == '.':
			print ('No')
			quit()
	
	if y > 0:
		if table[y-1][x] == '.':
			print ('No')
			quit()
	
	if y >= H:
		if table[y+1][x] == '.':
			print ('No')
			quit()
			

for y in range(H):
	for x in range(W):
		check(x,y)

print ('Yes')		
