GR translation: hair smocks

[Mike Jing]

V5.20-26, P5.35-41   Bloat is one of the co-tenants of the place, a
maisonette erected last century, not far from the Chelsea Embankment, by
Corydon Throsp, an acquaintance of the Rossettis’ who wore hair smocks and
liked to cultivate pharmaceutical plants up on the roof (a tradition young
Osbie Feel has lately revived), a few of them hardy enough to survive fogs
and frosts, but most returning, as fragments of peculiar alkaloids, to
rooftop earth, . . .

What's a "hair smock" exactly? Is it a smock you wear when you are having a
haircut?