RHIZOMES 261 



in preparation for the more active growth and the 

 formation of the aerial shoots in the next spring. 



Roots are always produced on "rhizomes, either gene- 

 rally distributed on the surface or localized at the bases 

 of the aerial shoots (Fig. 41, B), or at the bases of foliage 

 leaves arising directly from the rhizome. Such roots, 

 arising directly from a stem, are sometimes called 

 adventitious roots as opposed to the taproot and its 

 branches, which in rhizome-growing plants are short- 

 Uved. Organic food materials (starch or oil — sometimes 

 sugar — and proteins) are stored in rhizomes during the 

 winter, and are " mobihsed," i.e. converted into soluble 

 forms when new growth takes place. 



Rhizomes may be short and compact, the axis of the 

 rhizome shoot being then usually vertical or oblique 

 and growth being very slow (" male fern," dandelion, 

 plantain) ; or they may be elongated and horizontal, 

 often running for considerable distances below the 

 surface of the soil (Figs. 40, B, 41). It is this type of 

 rhizome, with brown or dingy coloured surface, from 

 which the name (meaning " root-like organ ") is taken. 

 But rhizomes are quite sharply distinguishable from 

 roots because they bear leaf structures and have the 

 anatomical construction of stems, not of roots. The 

 spread of many plants, such as sedges, rushes, some 

 grasses (e.g. couchgrass or " twitch "), is due to this type 

 of rhizome, which grows and branches freely, sending 

 up aerial shoots from the upward turning terminal, 

 or from lateral buds. Stolons or runners are very 

 thin, horizontal, quickly growing shoots, which run 

 usually upon the surface of the soil (e.g. strawberry 

 runners), and do not bear roots. The terminal bud 

 eventually turns up, thickens, produces a rosette 

 of foliage leaves, strikes roots down into the soil, 



