THE STEM, OR ASCENDING AXIS. 37 



called tendrils, it ascends trees and other objects to a great height, as 

 the grape, gourd, and other climbing vines. 



Vines. 48, Passion-flower (Passiflora'Iutea) climbing by tendrils. 49, Morning-glory, twining 

 from right to left 50, Hop, twining from left to right. 



179. THE TWINING VINE, having also a length greatly disproportioned to its dia- 

 meter, supports itself on other plants or objects by entwining it-self around them, 

 being destitute of tendrils. Thus the hop ascends into the air by foreign aid, and 

 it is a curious facfc that the direction of its winding is always the same, viz., with 

 the sun, from left to right ; nor can any artificial training induce it to reverse its 

 course. This is a general law among twining stems. Every individual plant of 

 the same species revolves in the same direction, although opposite directions may 

 characterize different species. Thus tho morning glory revolves always against the sun 



180. THE FORMS OP SCALE-STEMS are singular, often distorted in 

 consequence of their underground growth and the unequal development 

 of the internodes. They commonly belong to perennial herbs, and the 

 principal forms are described as follows ; but intermediate connecting 

 forms are very numerous and often perplexing. 



181. THE CREEPER is either subaerial or subterranean. In the former 

 case it is prostrate, running and rooting at every joint, and hardly dis- 

 tinguishable otherwise from leaf-stems, as the twin-flower (Linnaea), the 

 partridge-berry (Mitchella). In the latter case it is more commonly 

 clothed with scales, often branching extensively, rooting at the nodes, 

 exceedingly tenacious of life, extending horizontally in all directions be- 

 neath the soil, annually sending up from its terminal buds erect stems 



