MORPHOLOGY OF HIGHER PLANTS. 



325 



the flattened stems in the Cactaceae ; triangular in the Cyperaceae, 

 and quadrangular in the Labiatae and Scrophulariaceae. 



Hypogeous Shoots. While most stems attain a more or less 

 erect position, as in trees and shrubs, there are others which bend 

 over to one side, or lie prostrate on the ground, and in some cases 



FIG. 183. Polygonatum multiflorum, a plant growing in the Northern Hemispheres and 

 Japan and producing a rhizome resembling our Solomon's Seal (Polygonatum biftorum}. 

 A, rhizome placed artificially higher in the soil than the normal depth; its continuation 

 shoot has grown downwards. B, rhizome placed deeper than the normal depth; its con- 

 tinuation shoot has grown upwards. The dotted lines at n indicate the amount of annual 

 growth in the rhizomes A and B. C, a seedling rhizome. At the right is the seed, which 

 encloses the haustorial end of the cotyledon; H, primary root; n, lateral roots arising within 

 the axis of the shoot; a, posterior side of cotylar sheath; v, anterior side of the same; b, c, 

 katophyls (or leaves on hypogeous shoots) on the axis of the seedling. A and B, after 

 Rimbach; C, after Irmisch. (From Goebel's "Organography of Plants.") 



produce roots from the nodes, as in Mentha spicata (Fig. 184). 

 These latter are known as STOLONS or runners. 



Furthermore, the stems of a number of plants grow under- 

 ground, and these are known as RHIZOMES or ROOT-STOCKS (Figs. 

 182-190) ; from the upper portion of the nodes overground 

 branches arise which bear leaves (so that the work of assimilation 



