56 MONOCOTYLEDONE^E. 



and flowers are seated. The structure of the tuber 

 appears to be composed of a central part or pith, 

 within a soft bark-like integument, covered with a 

 thin cuticle, Fig. 24. Tubers are simple or compound ; 

 in the first, one principal gem or eye occupies the 

 crown, as in Cyclamen ; the second, besides a prin- 

 cipal, is studded with many smaller gems dispersed 

 over the whole surface, so that the smallest portion 

 separated from the main body will become a perfect 

 plant, as Leontodon Taraxacum. 



Fig. 24. 



Longitudinal section of a potato. 



Tubers are of many different forms : rotund, as 

 Crocus ; cylindrical, as Cochledria ; spindle-shaped, 

 as Dducus ; palmate, as Pceonia ; irregular, as Ane- 

 mone; beaded, as ArrJienatherum, Fig.25.; jointed, as 

 Nelumbium; bundled, as Georgina, &c. In duration, 

 tubers are annual, as Orchis; biennial, as Daucus ; 

 or perennial, as Cyclamen. They reproduce them- 

 selves above, as Gladiolus byzantinus ; laterally, as 

 Orchis ; and below, as some species of Arum. 



