Sentence:  Towards the tops of the stalks and branches come forth at every joint in the male <WSD>Mercury</WSD> two small round green heads, standing together upon a short footstalk, which growing ripe are the seeds, not having any flower. 
Meaning of the word marked with <WSD> tags:  (plant) An annual plant, annual mercury ("Mercurialis annua"), formerly grown for its medicinal properties; (French mercury), (herb mercury). (from 14th c.)