308 ON THE MATURATION OF GRAIN 



Next to crops of grain, as an article of food, 

 stands the crop of potatoes. And as they have 

 to store up and mature within their tubers, a 

 similar kind of matter for similar purposes, it 

 may be useful to enquire into their economy, 

 that we may thereby ascertain the proper time 

 for gathering them, to secure to ourselves their 

 full value. The tubers of potatoes, physiologically 

 speaking, are not of the nature of roots, as 

 generally supposed, but subterraneous stems. 

 Like stems, they therefore, bear buds, and 

 contain proper stores of material for the deve- 

 lopement of these buds ; but being only annual 

 in their duration, their tissues are chiefly cellular, 

 that they may contain such stores. In their 

 structure they are hence more analogous to 

 seeds, and the stores of material they contain in 

 a great measure similar. They, hence, undergo 

 like seeds, maturation, in order to make similar 

 provisions, and be similarly protected. What 

 changes they undergo, and what these provisions 

 are, we will now endeavour to ascertain. 



Potatoe plants have two seasons of growth 

 before maturation commences. During the first, 

 they develope their ryse or haulms, as axes of 

 vegetative gro\/th. After this full expansion of 



