Leaf of hemlock
This refers to the poison Socrates drank when he was sentenced to death by the Athenian assembly for impiety and corrupting the youth of Athens. By invoking the suicide of Socrates, Mr. Crawley presents himself as one who would stand by his ideals and would not take advantage of a chance to escape. Through this Classical allusion Mr. Crawley compares himself with Socrates, one who is wrongly charged and one who voluntarily undergoes punishment for the sake of upholding his principles. Perhaps Mr. Crawley over-dramatizes his predicament by making reference to the suicide of Socrates. [AM 2006]
A Latin masculine noun meaning “shepherd” or “herdsman.” In English, “pastor” refers to someone who is a minister or one who leads the congregation of a Christian church. [AM 2006]
Trollope seems to expect that English “pastor” will call up the associations of the Latin noun when he writes here of Mr. Crawley being a “spiritual pastor” set “over” his parishioners.