248 THE STORY OF PLANT LIFE 



A twining plant, Hop coils its stems around what- 

 ever support it can obtain. Darwin writes thus of 

 its habits : *' When the shoot of a Hop {Humulus 

 Lupulus) rises from the ground, the two or three first- 

 formed joints or internodes are straight and remain 

 stationary, but the next formed, whilst very young 

 may be seen to bend to one side and to travel slowly 

 round towards all points of the compass, moving, 

 like the hands of a watch, with the sun. The move- 

 ment very soon acquires its full ordinary velocity. 

 From seven observations made during August on 

 shoots proceeding from a plant which had been cut 

 down and on another plant during April, the average 

 rate during hot weather and during day is two hours 

 eight minutes for each revolution, and none of the 

 revolutions varied much from this rate." 



** The revolving movement continues as long as the 

 plant continues to grow, but each separate internode, 

 as it becomes old, ceg-ses to move." 



The rootstock is stout. The stem is rough, sticky, 

 with hairs with an anvil-like broad tip, and climbing, 

 tall, tough, with smooth branches. The climbing 

 hooks help to support the plant. The leaves are 

 opposite, stalked, heart-shaped, palmately three- to 

 five-lobed, the lobes ovate, with acute teeth, the 

 upper ovate, smooth, but rough above. The stipules 

 are connate. 



The first inflorescence is cymose. The plant is 

 dioecious. The male flowers are in loose panicles or 

 a much branched pseudo-panicle in the upper axils. 



