LECT. IV.] THE ROOT. TUBERS. 147 



intended to support these buds during their evolu- 

 tion and the earlier stage of their growth as plants; 

 and thence tuberiferous plants, which are chiefly 

 annuals, are perpetuated both by a lateral and 

 seminal progeny. In this respect the buds produced 

 on tubers resemble suckers ; differing from them 

 only in not being dependent on the original root for 

 their nutriment, but obtaining it from the tuber ; 

 and in separating spontaneously from the parent 

 plant, and becoming distinct, isolated beings. They 

 resemble seeds also, inasmuch as the gems upon 

 their surfaces are endowed with vitality, like the 

 embryon or plantule enclosed in the seed, and 

 remains latent, until the tuber be placed under 

 circumstances favourable for vegetation. 



Tubers are annual productions of the herba- 

 ceous part of the plant ; both the nutritious fecula 

 deposited within them, and the gems on their 

 surfaces, being formed from the descending or pro- 

 per juice, which, as you already know, is the sap, 

 or fluids taken up by the roots, changed by expo- 

 sure to the action of the air and the light in the 

 leaf. They are, in strict language, rather appen- 

 dages of the stem than of the root*; and are con- 



" remplies d'une fecule amilacee." Element de Phys. veg. t. i. 

 p. 90. 



* The following description by Dr. Darwin, of a variety of 

 the Potatoe raised in the garden of Major Trowel of Derby, 

 is a good illustration of this remark : " From one root there 

 " appeared to issue six or eight stems, three or four feet long, 



L2 



