n.填塞物；堵塞物；炮眼封泥
动词stem的现在分词形式.
The sap flowed out when he broke the stem of the flower. 他把花茎折断，汁液就流了出来。
The gardener could graft as many as twenty cuttings an hour on to briar stems. 这位园丁每小时可以嫁接多达20根枝条到石南茎上去。
