212 



HUTCHINSON'S POPULAR BOTANY 



FIG. 265. RHIZOME or SOLOMON'S SEAL. 



The cut-off base of this year's stem is shown just behind 



the growing point. Behind it the scars left by the decay 



of earlier stems. 



" Do take ij parties of the poudre of 

 gladen rotys [Iris roots], and the iij 

 part of the poudre of ellebre [Helle- 

 bore], that some men clepen cloff- 

 ynge, and medele both these poudres 

 togider in honey. A plaster of this 

 wole purge and dense the face of 

 frekels, also it will resolve the pockys 

 and whelkys of the face." 



Rhizomes haye a very important 

 function in that they enable plants to form vigorous colonies, which are 

 not only able to hold their own against the attacks of a competitive 

 species of plant, but enable the ovules of its individual stems to be more 

 certainly fertilized than would be the case were the individuals scattered. 

 A familiar instance is seen in the way the Common Daisy, having taken 

 advantage of a small bare spot on a lawn, proceeds to enlarge its 

 territory by sending out offshoots all around. Had it grown as a 

 single plant the summer growth of the neighbouring grasses would have 

 deprived it of light and air ; but if unchecked by the gardener the 

 Daisy patch extends, and, amalgamating with other patches, would soon 

 extirpate the grass. It is this method of spreading, too, that enables 

 the useful Marram of the sand-dunes to hold the loose sands together. 

 Other examples of this habit in common plants will be found in 



the Dog's Mercury and the Stinging 

 Nettle. 



Tubers are most conveniently 

 studied in the Potato-plant (Solatium 

 tuberosum, fig. 266). A potato is, in 

 fact, a true stem, and its "eyes" are 

 buds, each of which is capable of 

 producing a new plant. Thomas 

 Heriot (a fellow-voyager with Sir 

 Walter Raleigh, who was the first 

 to introduce the potato into this 

 country) describes the tubers as 

 "round, some as large as a walnut, 

 others much larger. They grow in 

 damp soils, many hanging together 

 as if fixed on ropes." The Jerusa- 

 lem Artichoke (Helianthus tuberosus) 

 and the Chinese Yam (Dioscorea 

 batatas, fig. 268) are other familiar 

 FIG. 266,-PoTATo-PLANT, examples of edible tubers. 



Showing underground portion of stem with tubers and n JL i j. 



root-fibres. Bulbs are subterranean stems not 



