import sys
n,w=map(int,input().split())
st=[[str(a) for s in b.strip()] for b in sys.stdin]
count=0
for i in range(1,n-2):
    for j in range(1,w-2):
        if st[i][j]=="#":
            count+=1
            if st[i][j]!=st[i-1][j] and st[i][j]!=st[i][j-1] and st[i][j+1]!=st[i][j] and st[i][j]!=st[i+1][j]:
                print("No")
                exit()
if st[0][0]=="#" and st[0][0]!=st[0][1] and st[1][0]!=st[0][0]:
    print("No")
    exit()

if st[0][w-1]=="#" and st[0][0]!=st[0][w-2] and st[1][w-1]!=st[0][w-1]:
    print("No")
    exit()

if st[n-1][w-1]=="#" and st[n-1][w-1]!=st[n-1][w-2] and st[n-1][w-1]!=st[n-2][w-1]:
    print("No")
    exit()
if st[n-1][0]=="#" and st[n-1][0]!=st[n-1][1] and st[n-2][0]!=st[n-1][0]:
    print("No")
    exit()
print("Yes")
