40 



MORPHOLOGY, OR COMPAEAT1VE ANATOMY. 



tion and habit of growth ; c./orw; d. condition of surface; e. ramification ; 

 and f. dimensions. 



a. Consistence. The terms herbaceous (Jierbaceus) and woody (lignosus) 

 need no further definition. Some stems are fleshy or succulent (carnosus\ 

 as in Cactus, &c. Most steins are solid (solidus) ; those of the majority 

 of Grasses and the Umbelliferae (Carrot, Celery, &c.) and the Horsetails 

 (Equisetum} are hollow or tubular (Jistulosus). 



b. Direction. Stems may be truly erect (strictm), flexuom (flexumus) 

 or nodding (nidans, cernuus). Stems which turn upwards from a horizon- 

 tal base are called ascending 



(ascendens) ; those lying along 

 the ground without rooting 

 are procumbent or prostrate 

 (decumbens, procumbens, hu- 

 mifusus) (fig. 39) ; if a pro- 

 strate stem roots at its nodes, 

 it becomes creeping (repens). 

 Slender stems neither lying 

 on the ground nor creeping 

 may be pendent (pendulous) 



Fig. 39. 



Procumbent stem of Thyme. 



when growing on rocks &c., and floating (Jluitans] when growing in 

 water. Weak stems also rise from the ground as climbing (scandens) or 

 twining (volubilis) stems. 



Climbing stems support themselves in various ways : the Ivy by tufts 

 of adventitious roots, which attach themselves firmly to foreign bodies ; 

 the climbing species of Clematis and the Canary-creeper (Tropceolumpere- 

 grinum) by hooking their leaf-stalks round the support ; other plants by 

 tendrils, as the Vine, Peas, Cucurbitaceze, &c. 



Twining stems coil themselves spirally round the supporting body, 

 turning sometimes in one direction, sometimes in the other, as in the Hop, 

 Convolvulus, Cuscutfij &c. If the direction from below is from the left 

 upwards to the right hand of the observer, supposed to be standing in the 

 position of the body around which the coil winds, the coil is said to be 

 dextrorse, if in the opposite direction sinistrorse ; but by some writers the 

 observer is supposed to stand in front of the coil, and then the application 

 tf the terms is reversed. Some of the tropical twiners produce woody 

 orunks resembling large cables. 



c. Form. The principal variations in form are designated by terms re- 

 quiring no explanation, such as cylindrical or terete, conical, columnar, &c. 

 If a stem presents thickenings 



Fig. 40. 



Fig. 42. 



opposite the origin of the leaves 

 (nodes), it is called knotted (no- 

 dosus) ; the reverse condition, 

 when there are constrictions at 

 intervals, is called jointed (articu- 

 latus). Other terms refer to the 

 shape as displayed in a cross sec- 

 tion of the stem. A stem is terete 

 (teres) when it presents a circular 

 section ; compressed (compressus) 

 when the section is elliptical ; angular when the section is polygonal, under 

 which head are distinguished, in a three-angled stem for example, trique- 



Fig. 40. A triquetrous stem. 



Fig. 41. A quadrilateral or square stem. 



Fig. 42. A ribbed stem. 



