SENSITIVENESS AND IRRITABILITY OF PLANT ORGANS. 161 



inedite, qu'il designe sous le nom d'Ypomcea sensitiva. Le 

 tissTi membraneux de la corolle campanulee, de cette plante 

 est soutenu par des filets on par des nervures qui, au moiudre 

 attouchement, se plissent ou ^'incurvent sinueusement, de 

 maniere a entrainer le tissu membrane iix 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'agir." * M. Dutrocbet 

 tben observes tliat tbis pbenomenon is in no way essentially 

 different from tbe closing of tbe corolla of Convolvulus, to 

 wbich Ypomcea is nearly allied, wben it passes into tbe sleep- 

 ing state, as does tbe calyx or periantb of tbe Nyctagineoe. 

 Lopezia coronata exbibits a curious and rapid movement 



a i c 



Fig. 48. — Lopezia (after Hildebrand). (For description, see text.) 



in a staminode. Miiller tbus describes it : f "In eacb flower 

 tbere is present one perfect stamen ; a second, standing 

 immediately below, is reduced to a spatbulate leaf, wbose 

 two balves fold upwards, and, in tbe first stage, projecting 

 borizontally from the flower, inclose tbe antber of tbe perfect 

 stamen (Fig. 48, a). Tbe stalk of tbe spatbulate leaf bas an 

 elastic tension downwards (b) ; tbe filament of tbe stamen 

 an elastic tension upwards (6), so wben an insect aligbts on 

 tbe projecting spoon-sbaped blade, as tbe only convenient 



* Recherches Anatomiques et JPhysiolngiques sur la Structure Intime 

 des Animaux et des Vegetaux et sur leur Motility, 1824, p. 64. 



t Fertilisation, etc., p. 265. 



