498 THE FERTILISATION OF FLOWERS. [PART I1I. 
363. LAMIUM INCISUM, Willd. :— 
Visitors: Hymenoptera—Apide; (1) Anthophora pilipes, F. 9 ¢ (19— 
21), ab. ; (2) Bombus pratorum, L. 2 (114); (3) B. Rajellus, Ill. 9 (12—138) ; 
(4) heute mellifica, L. % (6), all sucking normally ; (5) Halictus cylindricus, 
K. 9. (3), trying in vain to reach the honey. 
364, BALLoTA NIGRA, L.—The corolla-tube is only 7 mm. 
long ; above, it widens so little that a hive-bee can only insert 
the anterior part of its head, and can just reach the base of 
the flower with its proboscis, which is 6 mm. long. Two milli- 
metres from its base the tube is blocked by a ring of stiff 
hairs, which permit the bee’s proboscis to pass easily. They 
would suffice to exclude rain-drops, and are described by Sprengel 
Fic. 168.—Ballota nigra, L. 
i.—Essential organs of a young flower, viewed obliquely from the front (x 7). 
2.—Ditto, of an older flower. 
3.—Ovary (ov) and nectary (7). 
as serving that purpose; but as the horizontal position of the 
flower and its vaulted upper lip are sufficient protection against 
rain, their true use seems to be to exclude flies. Since flies pro- 
ceed irregularly for the most part in visiting flowers, those species 
whose proboscis is long enough to reach the honey of Ballota 
(Rhingia, Hristalis, etc.) might rob many flowers of their honey 
without fertilismg them; but the ring of hairs is sufficient to 
prevent the expanded end of a fly’s proboscis from entering. 
The under lip is marked with white guiding-lines which point 
towards the mouth of the tube; its broad central lobe serves as a 
landing-place, the clefts between it and the lateral lobes afford 
firm foothold for the forelegs and midlegs of the bee, and the 
lateral lobes with the groove between them, bounded by two 
longitudinal ridges, guide the bee’s proboscis. 
Decale, a v | 
