154 THE BOOK OF USEFUL PLANTS 



The effect of such growth is to make a bulb-like 

 vegetable out of the concentric leaf bases. Count 

 the leaves and you know how many layers there 

 are in the onion. 



One season's growth is needed to lay up store 

 of food in bulbs. So the onion rests over winter, 

 and if left where it grew, starts on its second 

 spring to use the store of fleshy leaf-bases to feed 

 one or more flower stalks which rise higher than 

 any leaves of the former season. These stalks 

 are hollow, green and swollen, but tapering to the 

 dense rounded cluster of lavender, or white flowers. 

 These are followed by seeds. After the seeds 

 ripen, the bulb is withered, the plant dead. 



Sometimes little fleshy bulbs appear instead of 

 flowers. These are constant in some varieties, 

 occasional in others. These are called "onion 

 sets." The flowers have been transformed into 

 bulblets from which full-grown onions grow the 

 following season. 



RHUBARB OR PIE-PLANT 



The druggist sells a bitter tonic extracted from 

 the rootstocks of a wild plant called rhubarb, 

 that grows in Thibet and northwestern China. 

 The acid of the sorrels is in the whole plant, which 



