bell glass 
noun
A bell-shaped glass cover used, especially formerly, as a cloche.Colonial gardeners also used cloches, or bell glasses, to nurture fragile seedlings and extend the growing season....
- Under this bell glass a fern spontaneously appeared, flourished, and eventually proved to be Doodia aspera.
- In the reception rooms of famous physicians bronze clocks usually stand under such bell glasses.
- keep one's head
- keep one's head above water
- keep one's head down
- keep one's mouth shut
- keep one's nose clean
- keep one's nose out of
- keep one's nose to the grindstone
- keep one's own counsel
- keep one's powder dry
- keep one's side of the bargain
- keep one's word
- keep (or archaic bear) someone company
- keep (or eat) kosher
- keep (or hold) one's end up
- keep (or leave) one's options open
- keep (or lose) one's cool
- keep (or lose) one's temper
- keep (or lose) track of
- keep (or make) a House
- keep (or sleep in) a whole skin
- keep (or stand) guard
- keep (or stay) out of someone's way
- keep out (or keep someone/thing out)
- keep pace with
- keep quiet (or keep someone quiet)