396 Chronicles of Science. [July, 



direction being towards the north. The circumstances seem to 

 contradict the prevalent theory that the deflection of plants from 

 the perpendicular is due either to the force of gravity, or to a desire 

 to seek the light. 



Sensitiveness of the Mimosa. — In the ' Memoires de la Soci^te 

 des Sciences Naturelles de Strasbourg,' M. Millardet details some 

 new and elaborate researches on the periodicity of the " tension " in 

 plants, especially in the Mimosa pudica, or sensitive plant. The 

 amount of " tension " is greater by night than by day, but under- 

 goes various oscillations of two kinds, which he terms periodic and 

 paratonic oscillations. The periodic oscillations are either long or 

 short, the longer lasting for twenty-four hours, and attaining their 

 maximum towards the end of the night, and their minimum towards 

 the middle of the day ; the shorter periodic oscillations lasting 

 about an hour, and occurring both by day and night. The para- 

 tonic oscillations are due to differences in light, temperature, 

 moisture, and other causes, and are more pronounced by day than 

 by night ; they are intermediate in duration between the longer and 

 shorter periodic oscillations. All these movements occur in both 

 stem and leaves. The motor organs of the leaves consist of tissues 

 which are subject to variations of tension, and the movements are 

 but an expression of these variations. 



Variegation and Double-flowering. — It had long been laid 

 down as a maxim by botanists that variegation of the leaves and 

 doubling of the flowers (conversion of stamens into petals) never go 

 together ; and although recent writers had doubted the universality 

 of the law, it was difficult to point to any authentic instances of the 

 two phenomena occurring together. Professor E. Morren, of Liege, 

 has, however, set the matter completely at rest by a description in 

 the ' Belgique Horticole,' accompanied by a drawing, of a double 

 wallflower with variegated leaves, which has been successfully grown 

 for some years by M. Eodigas of St. Trond. 



Irritability of Stamens. — M. Jourdain * has been trying experi- 

 ments on the effects of chloroform on the stamens of Mahonia, 

 which are excitable like those of the barberry, springing back against 

 the pistil when irritated. When enclosed in a glass bell, in which 

 was placed some cotton, on which a few drops of chloroform had 

 been sprinkled, at the end of one minute the stamens were strongly 

 thrown back as if in a tetanic state, and resisted all attempts at 

 excitation. Exposed again to free air, after eight or ten minutes 

 the irritability reappeared, at first feebly, and completely after the 

 lapse of twenty-five or thirty minutes. If the action of the chlo- 

 roform is continued for ten or twelve minutes the flower assumes 

 an orange tint, and the stamens do not recover their sensibility on 

 exposure to the air ; the next day they become black. 



* ' Comptes Rendus,' April, 25. 



