114 FORMS AND KINDS OF STEM. 
cases it becomes angular, and in some plants, particularly in 
those of certain natural orders, as the Cactaceze, Orchidacez, 
Euphorbiaceew, &c., it assumes a variety of anomalous forms. 
Thus in many epiphytical Orchids it becomes more or less® 
oval or rounded, and has received the name of Pseudobulb 
(fig. 256, b, b) ; in the Melon-cactus it is globular ; and in other 
Cacti it is columnar, more or less flattened, or jointed. In the 
Tortoise or Elephant’s-foot Plant (Testudinaria elephantipes), it 
forms a large rough irregular mass. 
WiG.w220: Fic. 226. Figs 22% 
Fig, 225, Climbing stem of the 
Ivy. a, a, Aerial roots. 
Fig. 227, Twining stem of a 
species of Convolvulus, 
Fig, 226. Twining stem of Honeysuckle, 
In general, stems possess a firm texture, and can therefore 
readily sustain themselves in an upright position ; but at other 
times they are too weak to support themselves, and then either 
trail along the ground, or attach themselves to some other plant 
or neighbouring object. In such cases, if they trail on the 
ground, they are said to be procwmbent or prostrate ; or if when 
thus reclining they rise towards their extremity, they are decwm- 
bent ; or if they rise obliquely from near the base, ascending. 
But if, instead of resting on the ground, they take an erect 
position and cling to neighbouring plants or other objects for 
support, they are called climbing if they proceed ina more or less 
