996 SmiMA-RY OF CtmRENT RESEARCHES RELATmO TO 



accordance with a principle applicable in common to the excitable 

 Btructurcs of jilauts and animals, viz. that the property which renders 

 a structure capable of undergoing excitatory change is expressed by 

 relative positivity, the condition of discharge by relative negativity. 



All these changes depend, in the author's opinion, on a difiference of 

 physiological activity between adjacent excitable cells or strata of cells 

 of which the protoplasmic linings are in continuity. 



Case of Abolition of Geotropism.* — M. P. Duchartrc observed that, 

 out of a dozen seeds of Phascohis multijiorus sown at the same time, the 

 germination of one was very abnormal. At the cud of several days a 

 small body was seen to project from this seed above the soil. This 

 body elongated vertically ; then, upon four equidistant longitudinal 

 lines, small iirotuberances were formed. The author then recognized it 

 to be the railicle of the embryo. He allowed it to grow for about two 

 months, and then examined it anatomically, an account of which is 

 included in the paper. 



Studies in Vegetable Biology. f — Mr. S. Le M. Moore continues his 

 observations on the influence of light uj)on protoplasmic movement. 

 After making various experiments with Selaginella Martcnsii and other 

 plants, the author states that we are justified in concluding that intense 

 light and prolonged darkness act in precisely the same manner upon 

 chlorophyll-bodies ; and it appears also that, paradoxical though it may 

 sound, fragmentation and condensation are really the same phenomenon, 

 the only ditference between them being that in the former condeusation 

 is more violent along certain lines than along others, thus entailing 

 disruption, whereas in the latter it proceeds equally all round. 



The author then makes s ime further observations on photolysis. In 

 those epidermal cells whicb are well provided with apparently healthy 

 chlorophyll without starchy contents, the deficient factor is proto- 

 plasmic energy ; and if this be correct, the failure of photolysis to come 

 oflf in epidermal issues is easily understood. At any rate, it is submitted 

 that, in view of its inability to stand the crucial test here applied to it, 

 the "activity" doctrine should heucefortli be dismissed from vegetable 

 physiology. 



The author then makes some observations on the behaviour of the 

 chlorophyll-plate of Mesocarpus with regard to light. (1) In diffused 

 light the chlorophyll-plate of Mesocarpus sets itself so as to cut the 

 greatest number of light-rays of the highest intensity. (2) In weak 

 sunlight the plate turns edge up. (3) The plate can be negatively 

 apostrophized. (4) When the turning movement is in jirogress, it will 

 not be stopped in the dark if light have imparted sufficient impetus to 

 the plate. (5) In darkness the plate may turn so as to remain either 

 face up or on its edge. 



He then goes on to discuss the lateral position of the chlorophyll of 

 palisade-cells. The capacity of light to modify the form of palisade- 

 cells is admitted on all hands. This granted, what difficulty is there in 

 conceiving that the form of all cells in direct relation with light is 

 so ordained by this agency, as to insure, upon simple mechanical prin- 

 ciples, the maximum exposui-e of the protojilasm to favourable, and its 

 minimum exposure to unfavourable (positive) grades of illumination ? 



* Bull. Soc. Bot. France, xxxv. (1888) pp. 266-71. 



t Jouni. Linn. Soc. (Bot.), xxiv. (1888) pp. 351-86 (3 pis.).., 



