PART IIL. | THE MECHANISMS OF FLOWERS. 191 
flower passes from the young, closed state (Fig. 62, 5) to the half- 
opened state (Fig. 62, 6); if we press a little harder, the split 
passes forward beyond the tip of the style (Fig. 62, 8), and in the 
“same instant the column flies upwards to the vexillum, scattering 
-a cloud of pollen, and the alz and carina spring down into the 
vertical position. 
If an insect performs the above operation while standing on the 
alz and thrusting its head beneath the vexillum, the column is pre- 
vented from springing up to its full height; it cannot scatter a cloud 
of pollen into the air, but the ascending style forces its stigma and 
instantly afterwards the mass of pollen against the under side of 
_ the insect. If the insect has been dusted with pollen in a pre- 
¢ viously visited flower, cross-fertilisation is thus effected ; if not, the 
_ stigma is dusted with its own pollen as the insect creeps backwards 
: out of the flower. Whether self-fertilisation occurs in absence of 
insects is a point that has still to be settled by experiment. 
_ Specimens with young virgin flowers which I left standing in 
water for over fourteen days withered without either exploding 
or producing seed. 
Since the flowers contain no honey, and expend all their pollen in 
_asingle explosion, after which the staminal column and style are 
concealed by the vexillum which closes over them as in the bud, 
. peey.can only offer attractions for pollen-collecting insects, viz. : 
female bees busy with the care of their young ; and even these are 
only permitted a single visit. The flowers, however, are visited by 
very various insects, which fly away after a vain attempt to obtain 
pollen or honey, I observed the following visitors in sunny weather 
in July, 1869, on a stretch of land covered with G. tinctoria near 
- Brilon and Warstein :— 
+4 a Hymenoptera—(a) Apide : (1) Megachile circumcincta, K, ?, very ab., 
.; (2) M. centuncularis, L. 9, very ab., c.p.,—the males occasionally ek 
in Bin for honey ; (3) M. villosa, Behunok. 2, one specimen, c.p.; (4) M 
versicolor, £ Em. ?, freq. ; (5) M. Willughbiella, K. ¢; (6) Diphysis sentatalen, 
Pz. $; (7) Anthidium punctatum, Latr. ¢,—the last three come in vain 
arch for honey ; (8) Apis mellifica, L. §, ab., c.p. ; (9) Bombus terrestris, 
9 , scarce, ¢.p. ; (10) Colletes Davieseana, K. 2, .p. ; (11) Andrena albicrus, 
| K. ¢; (12) A. fulvescens, Sm. ¢,—both vainly seeking honey; (13) A 
of hae ¢ ; (14) A. fulvicrus, K. 2; (15) Halictus rubicundus, Chr. @ ; 
¢ 6) H. albipes, F. 9; the last four scarce, »c.p. (all, including the honey- 
seeking males, caused the flowers to explode, and effected cxbas feat Taal: (b) 
Vespide : (17) an bealyy trifasciatus, F. 9. B. Diptera—(a) Conopide : (18) 
) Sicus ferrugineus, L.; (19) Myopa testacea, L. ; (b) Syrphidw: (20) Chryso- 
_ toxum pbicinctum, LC. Lepidoptera—Rhopalocera ; (21) Satyrus Megeera, 
{- 
if 
ie 
if 
