Theophrastus was much less concerned with formal causes than Aristotle was, instead pragmatically describing how plants functioned.
θiːəfɹˈæstəs wʌz mˈʌtʃ lˈɛs kənsˈɜːnd wɪð fˈɔːɹməl kˈɔːzᵻz ðɐn ˈæɹɪstˌɑːɾəl wʌz, ɪnstˈɛd pɹæɡmˈæɾɪkli dᵻskɹˈaɪbɪŋ hˌaʊ plˈænts fˈʌŋkʃənd.