100 OEGANOGEAPHY. 



accessory buds. In some trees, such as the Pir and Ash, these 

 accessory buds, instead of forming separate branches, become 

 more or less united, and the branches thus produced assume a 

 flattened or thickened appearance. Such branches are com- 

 monly called fasciated. These branches may however be pro- 

 duced by a single bud developing in an irregular manner. 



Besides the above three principal sources of abnormal or ir- 

 regular development of the branches, other minor ones arise 

 from the formation of extra-axillary branches in other ways than 

 those just alluded to. Thus the stem may adhere to the lower 

 part of thfi branch, which thus appears to arise from above the 

 axil of the leaf; or to the petiole or leaf-stalk, when it appears 

 to arise from below it. Other irregularities also occur, but they 

 are of little importance compared to those already mentioned. 



3. Of the Forms and Kinds of Stems and Branches. — In 

 form the stem is usually more or less cylindrical, while in other 

 cases it becomes angular, and in some plants, particularly in 

 those of certain natural orders, it assumes a variety of anomalous 

 shapes. Thus in many Orchids it becomes more or less OA^al or 

 rounded, and has received the name of Pseudobulb ; in the Melon- 

 Cactus, globular ; in other Cacti, columnar, more or less flat- 

 tened, or jointed. In the Tortoise^or Elephant's-foot Plant 

 {Testudiiiaria elephantipes), it forms a large rough irregular 



4 



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In general, stems possess a firm texture, and can therefore 

 readily sustain themselves in an upright direction ; at other 

 times they are too weak to support themselves, and thus require 

 the aid of some other body. In such cases, if they trail on the 

 ground, they are jprocumbent or prostrate ; if when thus reclining 

 they rise towards their extremity, they are decumbent; or if they 

 rise obliquely from near the base, ascending. Some weak stems, 

 instead of resting on the ground, take an erect position and 

 cling to neighbouring objects for support. Such are called 

 climbing or scandent if they proceed in a more or less rectili- 

 neal direction, as in the Passion-flower {fig. 201), where they 

 cling to other bodies by means of little twisted ramifications 

 cafled tendrils, v, v; or in the Ivy, where they emit little root- 

 like processes from their sides, by which they adhere to neigh- 

 bouring bodies {fig. 195, a, a). But if such stems twist round 

 other bodies in a spiral manner they are said to be twining ; and 

 this twining may take place either from right to left, as in some 

 Convolvuli {fig. 197), in the French Bean, and Dodder ; or from 

 left to right, as in the Honeysuckle {fig, 196), Hop, and Black 

 Bryony ; or first in one direction and then in another, irregu- 

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

 plants of cold and temperate regions are generally herbaceous 

 or die annually, although we have exceptions in the Vine, 

 Clematis, and Honeysuckle, which have woody stems ; in this 



