290 



AMERICAN HOMES AND GARDENS 



July, 19 10 



Timing the Rapidity of the Leading Traveling Bean Shoot 



By S. Leonard Bastin 



IHERE are few things more strange than 

 the means employed by the plant to get up 

 in the world. Each member of the vegeta- 

 ble kingdom has but one object, and that 

 is to secure a position above its neighbor, 

 so that it may enjoy to the full the light 

 and air above. Certainly the most inter- 

 esting of the methods adopted by plants to get the better of 

 one another, are those evidenced by the climbing species, 

 amongst which the bean stands out as a particularly strik- 

 ing example. It is possible to conduct a most instructive 

 series of experiments with this plant, as it is one of those 

 accomodating species which can be easily grown to demon- 

 strate the manner in which a typical twining plant behaves. 



The seeds of the French Bean can be induced to germinate 

 at almost any time of the year, if they are kept in a warm and 

 moist condition. They are perhaps most quickly stirred into 

 life by being placed in some damp moss, which is covered 

 up so as to exclude the light. As soon as the seeds have 

 started developing their second pair of leaflets, the small 

 plants may be placed into suitable pots. It is well to have 

 several specimens so as to guard against disappointment 

 through some of the examples going wrong. 



The early history of the bean is very much on the same 

 lines as that of any other plant. At first the seedling is pro- 

 vided with a sturdy stem quite strong enough to maintain 

 the plant in an upright position. When the second pair of 

 leaves are in an advanced stage, a very remarkable change 

 comes over the bearing of the plant. The young shoot 

 begins to grow very rapidly, extending at a rate of several 

 inches in the twenty-four hours. Meanwhile, the stem loses 

 a good deal of its bearing, and becomes weak and unable to 

 support itself in an upright posture. Now begins a very 

 wonderful chapter in the life of the bean, and a most critical 

 one, too. If the stem of the plant is not able to keep erect 

 at this juncture, it will be still more difficult for it to do so 

 later on when the growth will have extended many feet. It 

 therefore becomes a matter of instant importance to find 

 some support, and to this end a very surprising tendency 

 comes into operation. 



The first sign of the change in the bean is to be observed 

 by watching the leading shoot. This will be leaning over, 

 almost at right angles from the stem. It will be seen that the 

 tip of the shoot does not always point in the same direction, 

 but it is constantly changing its position. One is, in fact, 

 witnessing the commencement of that habit of growth which 

 is known as circumnutation. This is one of the most curious 



phenomena to be seen in the plant world, and although we 

 may realize the purpose served by the tendency, the charac- 

 teristic is not very easy to explain. The most obvious change 

 as it affects the plant, is that the stem is enabled to travel 

 round continuously, whilst the tip of the shoot leans over 

 as if it were searching for some object, on which it may find 

 a hold. It is a really very impressive spectacle to watch the 

 bean shoot sweeping round the course prescribed, at every 

 round leaning yet further out, for at this stage the actual ex- 

 tention of the stem is very rapid. Nor is the moving shoot, 

 which invariably travels from left to right, to be diverted 

 from the course which it pursues. The influence of light on 

 one side, so quick to affect the ordinary plant, makes not the 

 smallest difference to the traveling bean shoot. Even if the 

 twining portion be bound continuously in an opposite direc- 

 tion the result is all the same ; nothing will coerce the plant or 

 induce it to alter its course. Before this wonderful spectacle 

 even the most deeply learned scientists are completely 

 baffled; the secret of how the bean maintains its never ending 

 movement being one which hitherto has not been discovered. 

 The most that can be said is that the living matter in the 

 plant has been endowed with an inherent tendency to twist 

 and twine, and this instinct is handed down from one genera- 

 tion to another. 



To see the circumnutation of the bean at its best it is 

 necessary to have the plant in a very warm room, supposing 

 the experiment is conducted during the winter. All these 

 plant phenomena are carried on much more energetically 

 when the temperature is fairly high, than in a chilly atmo- 

 sphere. In the most favorable circumstances, even though 

 one cannot quite see the shoot traveling, yet the movement 

 is very rapid for a plant. In a particular case it was found 

 that the shoot traversed the circle in a little over two hours, 

 and by measuring the length of the portion of stem leaning 

 away from the axis it was found that the circumference fell 

 very little short of two feet. Thus it may be said that 

 roughly the tip moved at the rate of about an inch in five min- 

 utes — a wonderful accomplishment for a vegetable. This 

 was achieved in a moderate temperature, and during one 

 very hot day, the pace was even accelerated so that the circle 

 was traversed in little more than an hour and a half. Thus 

 the circling process will be continued, each hour the revolv- 

 ing shoot stretching out yet farther and thus Increasing the 

 probability that it will come into contact with some object. 



As soon as the circumnutation has been fully observed it 

 is interesting to have an opportunity of seeing the behavior 

 of the bean shoot when it comes towards a support. In a 



1 P. M. 



1.30 P. M. 



2 P. M. 



10 A. M., second day 



