58 



ESSENTIALS OF- BOTANY 



Fig. 31. Rootstock of Cotton-Grass {Eriophorum). 



of the hop (Fig. 30) ; others, 

 as the morning-glory, tak- 

 ing tlie opposite course.^ 



76. Underground Stems. 

 — Stems which lie mainly 

 or wholly underground are 

 of frequent occurrence and 

 of many kinds. 



In the simplest form of 

 rootstock (Fig. 31), such as 

 is found in some mints and 

 in many grasses and sedges, 

 the real nature of the creep- 

 insr undero-round stem is 

 shown by the presence 

 upon its surface of many 

 scales, which are reduced 

 leaves. Rootstocks of this 

 sort often extend horizon- 

 tally for long distances in 

 the case of grasses like the 

 sea rye grass, which roots 

 itself lirnily and thrives in 

 shifting sand-dunes. In 

 the stouter rootstocks, like 

 ,/, that of 

 the iris 

 (Fig. 32) 

 and the 



1 See Sti-asburger, Noll, Schenk, and Karsten's Text-Book, pp. 257-260 ; 

 also Vines, Students' Text-Book of Botany, London and New York, 1894, 

 pp. 759, 760. 



