Why doesn't openwrt register its hostname with another openwrt's dnsmasq?

Question

Domain Name System

Given a network 192.168.237.0/24 and two routers mercury and pluton. The gateway to the Internet is mercury, dnsmasq is running on it, which gives the settings for my smartphones, laptops and other equipment without any problems and simultaneously registers their hostname in its direct browsing zone. pluton is a dhcp client. Both routers are openwrt. Here is a fragment of the pluton config:
config 'interface' 'lan'
option 'type' 'bridge'
option 'ifname' 'eth0.0'
option 'proto' 'dhcp'
And here is the build from /tmp/dhcp.leases on mercury after registration pluton:
1450065219 bc:ae:c5:c4:6d:57 192.168.237.171 * 01:bc:ae:c5:c4:6d:57
Here is another device as seen hostname in place:
1450065095 78:92:9c:a8: 6e:38 192.168.237.
As a result, nslookup pluton says can't find pluton.
Where to dig?