Mournful or sad; often associated with melancholia induced by too much alcohol.
Being rational; the novel is at pains to point out that much of what we do and consider reasonable is in fact merely habitual.
A sense of liberation, as in "I think it may have come from a sense of facing something quite new and fresh to me" (p. 60)
The genetically engineered plant, quite probably of Russian origin, which gives the book its name, and its villain.