SENSITIVENESS AND IRRITABILITY OF PLANT ORGANS. IGl 



ineclite, qu'il dcsigne sous le nom d'Ypomcea sensitiva. Le 

 tissu membraneux de la corolle campanulee, de cette plante 

 est soutenu par des filets ou par des nervures qui, au moindre 

 attouchement, se plissent ou sHncurvent sinueusement, de 

 maniere a entrainer le tissu membi'aneax de la corolle, 

 laquelle, de cette maniere, se ferme completement ; elle 

 ne tarde point a s'ouvrir de nouveau lorsque la cause qui 

 avait determine sa plicature a cesse d'agii\" * M. Dutrochet 

 then observes that this phenomenon is in no way essentially 

 different from the closing of the corolla of Convolvulus, to 

 which Ypomasa is nearly allied, when it passes into the sleep- 

 ing state, as does the calyx or perianth of the Nyctaginece. 

 Lojoezia coronata exhibits a curious and rapid movement 



a i c 



Fig. i9.—Lopezia (after Hildebrand). (For description, 6ee text.) 



in a staminode. Miiller thus describes it : f "In each flower 

 there is present one perfect stamen ; a second, standing 

 immediately below, is reduced to a spathulate leaf, whose 

 two halves fold upwards, and, in the first stage, projecting 

 horizontally from the flower, inclose the anther of the perfect 

 stamen (Fig. 48, a). The stalk of the spathulate leaf has an 

 elastic tension do^vnwards (6) ; the filament of the stamen 

 an elastic tension upwards (6), so when an insect alights on 

 the projecting spoon-shaped blade, as the only convenient 



* Recherches Anatomiques et Thy siolngiques sur la Structure Intime 

 des Animaux et des Ve'getaux et sur leur Motility, 1824, p. 64. 

 t Fertilisation, etc., p. 265. 



