38 MANUAL OP BOTANY 



Tortoise or Elephant's-foot Plant {Tesiudinaria elephantvpes), it 

 forms a large rough irregular mass. 



In general, stems are strong and rigid, and can therefore 

 readily sustain themselves in an upright position ; but many are 

 too weak to support themselves ; these either trail along the 

 ground, or attach themselves to some other plant or neighbour- 

 ing object. Those which trail on the ground are said to be 

 procumbent or prostrate ; if when thus reclining they rise to- 

 wards their extremity, they are decumben i ; if they rise obliquely 

 from near the base, ascending. Those which cling to neigh- 

 bouring plants or other objects for support are called climbing 

 if they proceed in a more or less rectilinear direction, as in the 

 Passion-flower, where they adhere to other bodies by means of 

 little twisted ramifications called tendrils, or in the Ivy, where 

 they emit little aerial roots from their sides, by which they 

 cling to neighbouring bodies (jig. 50, a, a). If such stems twist 

 round other bodies in a spiral manner, they are said to be 

 tivining ; and this twining may take place either from right to 

 left, as in some Convolvuli (fig. 52), French Bean, and Dodder ; 

 or from left to right, as in the Honeysuckle (fig. 51), Hop, and 

 Black Bryony ; or first in one direction and then in another, 

 irregularly, as in the White Bryony. The climbing and twining 

 stems of cold and temperate regions are generally herbaceous 

 or die annually, although we have exceptions in those of the 

 Ivy, Clematis, and Honeysuckle, which are woody. In tropical 

 climates these woody climbing and twining stems often occur ; 

 they are called lianas or lianes, and they frequently ascend to 

 the tops of the loftiest trees, and then either descend to the 

 ground again, or pass to the branches of neighbouring trees. 



The stem has received many names according to its nature. 

 Thus it is called a caulis in plants which are herbaceous, or die 

 down annually to the surface of the ground; a trunlt, in trees, 

 where it is ■\\-oody and perennial ; a culm, in most Grasses and 

 Sedges, where it presents a jointed appearance ; and a caiidex 

 or stipe, in Tree-ferns and Palms. 



Herbs, Shrubs, and Trees. — From the natm-e, duration, and 

 mode of branching of stems, plants have been arranged from the 

 earliest periods in three divisions, called, respectively. Herbs, 

 Shrubs, and Trees. Those plants which have stems that die 

 down annually to the surface of the ground are called herbs ; 

 while those with perennial aerial woody stems are denominated 

 trees or shrubs according to circumstances, as described below. 

 Herbs are also further characterised as annual, biennial, and 



