BEHAVIOR OF ASPARAGUS PLUMOSUS 67 

 IV. PHENOMENA OF CLEVIBING 



Until the plant has grown to a considerable height, 30 cm. 

 or more, the shoot does not show circumnutation. With the 

 inception of circumnutation, the plant is ready for climbing. 

 About such a support as twine or a fine wire it twines with a 

 close spiral. Just before the definitive growth is attained, 

 the tip of the main axis bends outward and assumes the final 

 diageotropic position. 



Numerous tests were made to determine whether the cUmb- 

 •ing shoot was sensitive to contact. Cords and thin rods were 

 placed in contact with the various flanks of the climbing shoot, 

 but no indication of sensitiveness to contact or pressure was 

 perceived. 



V. SUISIMARY 



The shorter, non-twining aerial shoots of Asparagus plumo- 

 sus show a vertical proximal portion and a horizontal distal 

 portion which are nearly equal in length. The most of the 

 branches of the main axis are borne on this horizontal portion, 

 and all of these branches, whether of the first or higher order, 

 are spread out in a horizontal plane. 



This bending of the main axis to the horizontal is generally, 

 if not always, started by the heliotropism of the shoot carry- 

 ing the member out of the perpendicular. As the shoot nears 

 the cessation of growth, it reverses its response to gravitation, 

 changing from negative geotropism to diageotropism. 



The branches of the main axis also become diageotropic, 

 but their tropic behavior toward light and gravitation has not 

 been very full}' studied. 



Though the apical portion of the aerial shoot with its branches 

 becomes a horizontal, flattened frond, it still remains, both 

 morphologically and physiologically a radial member. When 

 the plant is inverted, and the previously lower side is made 

 the upper, there is no response on the part of the plant tending 

 to reverse the sides. Main axis and branches seem to be just 

 as much in equihbrium as before. 



