77.] FORMS OF THE LEAF-BEARING STEMS. 91 



the branches, and runs through to the summit, as in 

 the Beech, Birch, Oak, and especially in the -Spruce 

 trees with oval or pyramidal forms. But in the other, 

 the DELIQUESCENT AXIS, as seen in the Elm and Apple- 

 tree, the trunk suddenly divides into several subequal 

 branches, which thence depart with different degrees 

 of divergency, giving the urn form to the Elm, the 

 rounded form to the Apple-tree, the depressed form to 

 the Sloe-tree (Viburnum) and Dogwood. 



227. CAUDEX is a term now applied to the peculiar trunk of the Palms 

 and Tree-ferns, simple, branchless columns, or rarely dividing in advanced 

 age. It is produced by the growth of the terminal bud alone, and its sides 

 are marked by the scars of the fallen leaf -stalks of former years, or are yet 

 covered by their persistent bases. Tln.^ stock or caudex of the cactus tribe is 

 extraordinary in form and substance. It is often jointed, prismatic, branched, 

 always greenish, fleshy, and full of a watery juice. Instead of leaves, its lat- 

 eral buds develop spines only, the stem itself performing the functions of 

 leaves. These plants abound in the warm regions of tropical America, and 

 afford a cooling acid beverage to the thirsty traveler when springs dry up 

 under the torrid sun. 



228. THE VINE is either herbaceous or woody. It is 

 a stem too slender and weak to stand erect, but trails 

 along the ground, or any convenient support. Some- 

 times, by means of special organs for this purpose, 

 called tendrils, it ascends trees and other objects to a 

 great height ; as the Grape, Gourd, and other climb- 

 ing vines. 



229. The twining vine having also a length greatly disproportioned to its 

 diameter, supports itself on other plants or objects by entwining itself around 

 them, being destitute of tendrils. Thus the Hop ascends into the air by for- 

 eign aid, and it is a curious fact 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 the 

 Morning-Q-lory revolves always against the sun, 



