PERCUSSIVE MECHANISM. 263 



As the two stamens are close together and the lower arms of the connective 

 practically touch one another, the upper arms fall simultaneously, and anyone 

 observing the phenomenon from the side might think there were only a single 

 rocking anther in the flower. Thus, when a humble-bee, making its way from 

 the landing-stage of the under-lip to the floral receptacle, comes against the pair 

 of short lever-arms barring the entrance, the anthers drop simultaneously upon 

 its back and cover it with pollen (271 ^). We shall show in a subsequent section 

 that bees laden in this manner rub the pollen off on to the deflexed stigmas of 

 the flowers they subsequently visit (271 ^). The hammer-apparatus in the flowers 

 of Salvia officinalis, which grows broadcast on the shores of the Mediterranean, 

 only differs from the above in that a little pollen is developed in addition at the 

 end of the lower arm of the lever, and is brushed off" on to the head of the insect. 

 The rocking part of the stamen in every species of Salvia must be looked upon 

 as an anther with a specially modified connective. The connective is transformed 

 into a long curved lever bearing an anther-lobe at each end. In Salvia glutinosa 

 only the lobe at the upper end is polliniferous, whilst at the lower extremity there 

 is a complete absence of pollen. In Salvia officinalis, on the other hand, a little 

 pollen develops, as we have seen, in the smaller lobe at the end of the shorter arm 

 also. In the numerous species of which Salvia pratensis is a type the filaments 

 are extremely short, and the lower arm of the lever in each case is metamorphosed 

 into a quadrangular flap or valve. The flaps of the two opposite stamens are 

 joined so intimately together that they close the mouth of the flower like a trap- 

 door. Each valve, however, has a little notch in the side adjoining the other, and 

 the two notches coincide so as to form an orifice in the middle of the trap-door. 

 Insects insert their probosces through this hole, and in so doing push the trap- 

 door backwards and upwards. The valves of the trap-door being also the short 

 arms of the lever-apparatus, their ascent is accompanied by the descent of the long 

 arms, each of which bears an anther-lobe full of pollen at its extremity, and in 

 this manner the upper surface of the insect's body is covered with pollen as it 

 sucks the honey. 



In the Lopezias indigenous to Mexico, the effect of the striking of insects by the 

 anthers is to load, not the upper, but the under surfaces of their bodies with pollen. 

 These plants {Lopezia coronata, L. miniata, L. racemosa) are remarkable for having 

 only a single anther-bearing stamen in each flower. The stamen is wedged in a 

 sterile, petal-like staminode inserted immediately below it; this staminode has its 

 free end fashioned into the shape of a spoon. This spoon-shaped extremity affords 

 the most convenient alighting-place, and the moment an insect settles upon it the 

 staminode suddenly flaps down, whilst at the same instant the stamen concealed 

 within it (being previously in a state of tension) springs up, striking the under 

 surface of the insect's body and covering it with pollen. 



The flowers of the Barberry (Berberis) have irritable filaments which cause the 

 anthers to strike against insects. There are six stamens arranged in two whorls 

 in each flower; they slope obliquely outwards, and are concealed in the concave 



