MODIFICATION OF FORM OR FUNCTION 1G5 



Acauh'scent Plants. — The term Acaiileseent, wliile strictly meaning 

 stemless, can, of course have no such ai^phcation, as all fiowering plants 

 possess a stem, even before germination occurs. The term is applied 

 to those plants whose stems arc so short as not to become con- 

 si)icu()us. 



The Crou'ii. — The stem of sudi a plant is called a ("rowii. The term 

 crown is also appUeil to the branching or leafy portion of any stem. 



Trees, Shrubs, and Vudcrshruhs. — A plant possessing a woody and 

 erect stem rising singly to the height of fifteen (according to some 

 authorities, twelve) feet or more is denominated a Tree, or Arborescent 

 plant, although the precise application of such a term is impossible. 

 A perennial woody stem which has not these characters is called a 

 Shrub or a Fruticose stem. Very small shrubs appearing on causal 

 insi)cction as herbs are called Undershrubs or Suffruticose plants. 



Direction of Growth and Nature of Support. — As to the direction of their 

 growth and the nature of their supjjort, stems may be Erect, in which 

 case they are erect through their entire length; Ascending, in which case 

 the base for a greater or less distance rests upon the ground, the terminal 

 portion becoming erect; Horizontal, in which case they are considered 

 as having no other support than the parent stem, from which they 

 extend at a right angle; Drooping, in which case they are first hori- 

 zontal, the outer portion becoming pendant; Pendant, or "Weeping," 

 when they are pendulous from their point of origin or almost therefrom; 

 Decumbent, when at first erect or supported by the i)arent, the outer 

 l)()rtion dechned so far as to rest upon the ground; Reclining, when 

 resting ui)on some means of sui)i)ort elevated above the earth, as over 

 the t()i)s or branches of other i)lants; ProcnmlxMit, when resting at full 

 length upon the ground witlioiit rooting at the joints; Repent, or 

 "Creeping," when ])rostr;itf and rooting at the joints (Fig. 445); 

 Twining, when sup])orting themselves by the twining of the stem itself 

 around a support; Climbing, when elevating and sui)porting them- 

 selves by other methods than a twining habit, the principal forms being 

 the Cirrhiferous, when climbing by tendrils (Fig. 4;-51), and Aculeate, 

 when cliinbiiig i)y hooks (Fig. 4;]()). 



Modification of Form or Function. — Mixli/ird Sfews. — As to modifi- 

 cation of form or function, stems arc snbj(>ct to a somewhat elaborate 

 classification. 



They may be modified for the ])uri)osc of defence, that is into thorns 

 or spines (Fig. l.").'i), altliongli not all thorns or spines arc transformed 

 branches. Some branches of this foi'ni remain so permani-ntly, while 



