PART III. | THE MECHANISMS OF FLOWERS. 471 
(11). L. albiceps, Mgn., the last four species not rare. B. Lepidoptera—Rho- 
palocera: (12) Satyrus Janira, L. All these insects sucked honey only, 
though I expected to see the Syrphide at least eating pollen. 
338. MENTHA AQUATICA, L. (IZ. hirsuta, Sm.).—W hile in Mentha 
arvensis small-flowered female and large-flowered hermaphrodite 
flowers occur in nearly equal numbers, in JZ. aquatica the former 
are much rarer than the latter. In the hermaphrodite flowers the 
tube is 4 to 5 mm. long, and about 2 mm. wide at the mouth; 
otherwise the flower resembles that of JZ. arvensis. Although, 
owing to the greater length of the tube, the honey is slightly less 
accessible than in JZ. arvensis, insect-visits are more numerous, 
owing to the taller stalks and the larger, denser heads of flowers. 
Visitors : A. Hymenoptera—(a) Apide : (1) Halictus cylindricus, F. ¢ ; (2) 
H. maculatus, Sm. ¢, both ab. ; (3) H. longulus,Sm. ¢; (4) H. nitidiusculus, 
K. g, all s. ; (b) Ichnewmonide : (5) Various sp., some creeping bodily into 
the flowers. B. Diptera—(a) Empide: (6) Empis rustica, Fallen; (7) E 
livida, L., both ab., s. ; (8) E. tesselata, F., do. ; (b) Syrphide: (9) Ascia 
podagrica, F., s. ; (10) Eristalis nemorum, L. ; (11) E. arbustorum, L. ; (12) 
E. eneus, Scop. ; (13) E. sepuleralis, L., all four very ab., sometimes s., some- 
times f.p. ; (14) Syritta pipiens, L., ab. ; (15) Helophilus pendulus, L., ab. ; 
(16) H. trivittatus, F.; (17) Syrphus pyrastri, L., ab. ; (18) Melanostoma 
mellina, L., ab., these also both s. and f.p. ; (¢) Muscide : (19) Onesia floralis, 
R. D. ; (20) O. sepulcralis; Mgn. ; (21) Sarcophaga carnaria, L. ; (22) Musca 
corvina, F’,, all four very ab. ; (d) Tabanide : (23) Chrysops cecutiens, L., s. 
Delpino considers Mentha and Coleus, Lour., degraded forms of 
the Labiate type (No. 178, p. 143; 360, p. 656); he, however, 
gives no reason for thinking them to be such, and not rather less 
specialised forms, differing less from the common ancestors of 
the Labiates. 
The flower of Coleus oe Benth. ?) is figured and described 
in No. 560, It. 
339. Lycopus EUROP&US, L.—The corolla forms a bell 3 to 4 
mm. long, 24 mm. wide at the mouth, but scarcely 1 mm. wide at 
the base. Honey is secreted by the yellow fleshy base of the 
ovary ; it is accessible to very short-lipped insects, and is sheltered 
from rain by long hairs which project from the sides of the bell 
towards its centre. Some purple spots on the under lip serve 
as guides, 
The flowers are markedly proterandrous. When the two 
anthers which project from the tube come to maturity, the two 
stigmas still lie folded together (Fig. 160, 1). When the stigmas 
