196 JOHN H. WILSON [march 



the leaflet of the Sensitive Plant, in so far that it does not respond un- 

 less it is touched in a certain place. It is an interesting test to bring 

 the point of a needle gradually downward, until it reaches the spot in 

 the filament where sensitiveness is located. The petals can be taken 

 away separately, each with a stamen attached, without causing move- 

 ment. If a stamen, still attached to the petal, is touched at the 

 sensitive point, it curves inwards suddenly, and after recovery will 

 bend again when stimulated. If separated carefully from the petal, 

 laid on a flat surface, and touched, the seat of movement is very clearly 

 demonstrated, the curvature being then seen to take place entirely at 

 the lower part of the filament. The bending is observed to be greater 

 in some species than in others. There is no response to stimuli when 

 the organs are in course of regaining their equilibrium. 



The copious supplies of nectar poured out from the glands which lie 

 at the base of the petals attract bees in numbers to the flowers. The 

 instant the proboscis of the bee is inserted, the stamens touched spring- 

 forward and cover the insect's head with pollen. In a second he is 

 off to plunder another flower, bearing the fertilising powder with him. 

 A clump of barberry is redolent of honey. 



While the stamens in the barberry fall forward, there are some 

 flowers in which they fall backward, when touched. The most easily 

 procured plant showing this is the rock rose (Helianthemum vulgare), a 

 low-growing, somewhat woody plant, common on grassy banks and 

 moorland spots. The centre of the yellow flowers is occupied by a 

 tuft of delicate stamens. They stand close together in the undisturbed 

 flower, but when touched at any point they spread out, and the pistil, 

 previously hidden, is then exposed. 



Quite a similar mechanism is seen in Sparmannia africana, a Cape 

 plant, having no immediate botanical relationship with our rock rose. 

 Occasionally seen in our greenhouses, Sparmannia is a shrub of con- 

 siderable size, with large hairy leaves and trusses of white flowers stand- 

 ing well above the foliage. The individual flowers rise from a pendent to 

 an erect position when about to open. The petals, four in number, are 

 pure white, with a pink spot and " guiding lines " at their base. They, 

 and the four narrow sepals alternating with them, surround the bunch 

 of brightly coloured stamens. The filaments, or stalks, of the outer 

 stamens are bright yellow, and beaded with curious undulate swellings 

 throughout their whole length. The outermost bear no anthers, and 

 terminate in a distinct purple point. The inner stamens, on the other 

 hand, have crimson filaments, with little or no beading, and they carry 

 large pollen-bearing anthers. Transition-forms between the two kinds 

 occur plentifully, the most interesting being such as bear the rudiments 

 of anthers. In the centre is the small superior, spherical ovary, sur- 

 mounted by the delicate style which is equal in length to the longest 

 stamens. The flowers have a faint odour, suggestive of whin blossom. 



When the day is sunny the flowers open well out, so that the 



