These two hosts are on the same vlan, therefore they should be able to communicate at L2 via their MAC addresses without routing.
They could communicate in L2 but they can't in L3. IP uses the local routing table before sending to find out how to send a packet. Since the destination is outside the local subnet, the use of a gateway is required - even though the destination is in the same L2 segment/VLAN, but IP simply doesn't know.
There are ways to get around this limitation: use a special routing entry (not supported on all platforms) or use a fake gateway with static ARP. But usually it's best to simply put neighbor hosts in the same subnet.
