lo Esther Pearl Hens el 



i. e., the concave side is passive. It is affected, later, as much by 

 temperature changes as the convex side. The second (the most 

 probable according to the author) is that the opposite sides react 

 in an opposite manner to temperature changes, the restraint of 

 the concave side being recognized as an active retardation in 

 growth. The third possibiHty is that the concave side is not 

 usually influenced by temperature changes. 



Reynolds Greene's view ( 1900) as to the nervous mechanism 

 of a plant is especially 'interesting, although flower movement is 

 not discussed by him in his Vegetable Physiology, in which the 

 former discussioii is given. He says that a plant has a nerv- 

 ous mechanism, and that stimuli are conducted from cell to cell 

 through the connecting strands of protoplasm which pass through 

 the cell walls, and contrasts this with the nervous system of ani- 

 mals. The root tip, at a short distance from the apex, the three 

 hairs on the leaf of "Venus' Fly Trap," etc., are special sense 

 organs or regions, which, however, are not anatomically dif- 

 ferentiated. The protoplasm in those parts receives the stimulus 

 due to the physiological differentiation of the protoplasm ; hence 

 plants can respond to a more delicate stimulus than animals. The 

 lack of coordination, however, may cause the stimulus to procKice 

 a harmful effect on the plant. 



J. Bretland Farmer, in an article which appeared in the New 

 Phytologist for March 19, 1902, refuses to accept the theory that 

 epinasty and hyponasty cause opening and closing of the tulip 

 flower. He attributes movement to a localized irritable tissue 

 (as in Dionaea) on the outer surface of the petals. This area 

 consists of active cells capable of altering their state of tur- 

 gescence, or, at any rate, their size, more readily and effectively 

 than the cells which form the more internal tissue layers. The 

 intercellular spaces are large in these perianth leaves, and the 

 cells so arranged that they give a certain amount of shearing 

 action without damaging the cells themselves. One experiment, 

 niade by Farmer, is to put a median longitudinal section in dilute 

 KNO.j solution, which causes the petals to straighten out (open). 

 To prove that there is an irritable tissue, he puts the petal in 

 water, when it closes, or, rather, curves in, then in alcohol to kill 



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