On the direction assumed by plants during their growth

Abstract

This paper is divided into three sections. The first section contains an account of some observations and experiments made by the author on the phenomena of the curling of the tendrils of the Tamus communis . After a description of the tendril, which in this plant is the footstalk of an abortive leaf, the author shows that the contractile power of the organ is excited by contact with any object whatsoever, and even with another part of the same plant; that the curling begins at the point of contact, but continues in both ends of the tendril, either forming knots, if there be something to embrace, or taking the shape of a cork-screw, if there be not. The knots are completed in a few minutes, and exert a considerable degree of pressure. A separation from the plant stops the curling up of the tendril. The curling always takes place in the same direction from the outside inwards. When the tendril is immersed in water, or in a solution of gum, it does not contract; but at the same time it does not lose the faculty of curling up by contact with a solid body. Ammonia, alcohol, or Eau de Cologne have little or no effect. Diluted sulphuric and nitric acids, even the vapours alone of the last, without actual contact, immediately excite in the tendril an energetic contraction. The same thing happens with a solution of corrosive sublimate. On the contrary, prussic acid stops the curling up that had already begun, and renders the tendril incapable of being again excited by the contact of a solid body.