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it can be made to continno doing so nntil it forms a curve or hook. 

 In ilr. Darwin's experiments tlie growing points of the seedlings 

 were made to impinge against a piece of smoked glass, and thus 

 the track of the progress of the roots was delineated. Beans were 

 allowed to germinate on bare sand, and after one had protruded its 

 radicle two inches, it was turned upside down, so that the radicle 

 was kept in damp air and now stood upright. A filament one inch 

 in length was affixed obliquely near its tip, and the movement of 

 the terminal bead was traced from 8.30 a.m. to 10.30 p.m. The 

 radicle at first changed its course twice abruptly, then made a 

 small loop, and afterwards a zigzag curve. These sevei'al cases of 

 the effects of contact, or other irritants, vapour, light, and the 

 attraction of gravity, being transmitted from the excited part for 

 some little way along the organ in question have an important 

 bearing on the theory of all such movements. 



Circumnutation, called by Sachs revolving nutation, is of 

 common occurrence, particularly amongst climbers ; it derives its 

 name from the well known fact that if we closely observe a twining 

 stem, the extremity of which points towards the north, it will be 

 found afterwards gradually to bend more and more eastward until it 

 faces that point, thence onwards to the south, and in succession to the 

 west, and round again to the north. If these movements are quite 

 regular the apex will have described a circle, or rather a circular 

 spiral. Even steins of seedlings, before they have broken through 

 the ground, as well as their buried radicles, circumnutate as far as 

 the pressure of the surrounding earth permits. In this universally 

 present action we have the basis of the most diversified movements 

 of the plant. Thus the stems of climbing plants, the position of 

 young leaves, the variations of their direction by night, or towards 

 the light, are all modifications of this law. In the hop the first 

 formed internodes are straight and remain stationary, but the next 

 formed, even when young, may be seen to bend on one side and 

 travel round all the points of the compass, and as the plant continues 

 to grow the axis of each iriternode becomes twisted, and then after 

 a time assumes a rigid form. A. curious point connected with this 

 twisting is that it is in direct proportion to the inequalities of, or 

 freedom from, support ; for the stem does not become twisted when 

 it is allowed to climb glass rods, but only rough sticks, or when 

 hanging free in the air. Mr. Darwin thinks the purpose of this 

 bending to all points is to find support, but that when this is 

 gained the motion is arrested. It is certain that the revolution is 

 not directed by the sun, for out of thirty-nine plants on which 

 observations were made, twenty-five revolved in opposition to its 

 course, and twelve towards it. 



Clematis glandulosa, climbs by its leading shoots, first in one 

 direction and then in another when allowed to ascend a perpen- 



