16 OKGANOGRAPHY AND GLOSSOLOGY. 



up the lower .portion of the stem; if the covering is slight, the tuber swells l.ut 

 little ; if the light can penetrate to the stem, the tuber becomes green, and produces 

 rosettes of leaves. 



Props (fulcra) are a kind of aerial roots which spring from the axils of leaves, 

 or from various points of the stem in certain climbing plants (Ivy, fig. 47), which 

 are attached by them to walls or trees ; these organs are non-absorbent, bnt under 

 suitable conditions they behave like ordinary roots, as is seen with ivy cultivated for 



edgings. 



Suckers (haustoria) are small warts upon certain parasitic stems (Cuscuta, 

 fig. 48), whence issue true supplementary roots, which attach themselves to the 

 neighbouring plants, and draw nourishment from their juices. 



The stem is cylinaiic or terete (c.. cylindricu*, teres), when a transverse cut 

 presents a circular outline (Cabbage); compressed (c. compressus), when an elliptic 



48. CtiBctitn. Stem with sticker* (map.). 40. Pink. Nodose stem. 



one, as if squeezed from opposite sides (67. John's Wort, Tutsan) ; triangular or 

 trigonous (c. triavgularis, trigonus), when a cut shows three sides (Carex) ; square 

 (c. guadrangularis, tetragonus), when it shows four right angles (Lamium) ; 

 pentagonal (c. quinquangularis, pentagonus), when it shows five faces and five angles 

 (Bramble), 



The stem is glabrous (c. glaber), when there are no hairs on it (Horse-tail) ; 

 smooth (locvis), when, being glabrous, it presents no roughness, and its surface is quite 

 even (Tulip) ; scabrous (c. scaber, asper), when its surface presents little inequalities 

 (Carrot) ; striate (c. stria tus), when it is marked with small raised longitudinal lines 

 or stria? (Sorrel) ; winged (c. alatus), when furnished with foliaceous expansions 

 (Comfrey, fig. 66) ; nodose (c. nodosus), when its nodes are tumid (Pink, fig. 49) ; 

 pilose (c. pilosus), when it is furnished with long scattered hairs 



