354 GENERAL BOTANY 



leaves which serve both for storage and for the support of aerial 

 parts growing from them. On account of their underground 

 habit they often become highly modified in both form and 

 structure. 



Runners and stolons are horizontal stems much like rhizomes 

 except that they run over the surface of the ground, in which 

 they frequently take root and give rise to new plants, as in the 

 strawberry (Fig. 76). Prostrate stems are like runners except 



that they rarely take root 

 in the soil over which 

 they trail. 



Bulbs like the onion 

 and tulip (Fig. 79) are 

 short, erect stems which 

 bear scalelike leaves filled 

 with reserve foods sur- 

 rounding a terminal bud. 



Corms are short, erect, 

 FIG. 207. Rootstock of Solomon's seal . ,. OAN 



fleshy stems (Fig. 80) 



&, &, buds; r, roots; s, flowering stem . , . . , 



with inconspicuous scale 



leaves. They usually have a prominent terminal bud and less 

 conspicuous lateral buds in the axils of the scale leaves. 



Tubers, like the potato (Fig. 78), are essentially greatly 

 shortened rhizomes with scale leaves and lateral buds. They 

 are usually filled with stored reserve food. 



Leaves. Fig. 208 illustrates certain characters of leaves, per- 

 taining to their form, margin, leaf tips, and venation, which are 

 of importance in characterizing and identifying plants. The 

 figures are self-explanatory, since the proper terms descriptive 

 of the leaves are used in connection with the figures. The 

 terms pinnate, palmate, and parallel, used in connection with the 

 leaf shapes, indicate the type of venation characteristic of each 

 leaf. Parallel venation is characteristic of such leaves as those of 

 the linear type, found in grasses and members of the lily family, 

 where the secondary veins run lengthwise of the leaf parallel 

 to the midvein. Pinnate and palmate venation are found in the 

 broad-leaved herbs and trees which belong to the dicotyledons. 



