CHAPTER VII 



LILIACEAE 



ALLIUM CEPA 



ALLIUM and Asparagus are important genera in the lily family, 

 and there are many ornamental plants in this group, including 

 species of Lilium, Tulipa, and Hyacinthus. . In the genus Allium, 

 there are a number of strong-scented, pungent herbs characterized 

 by the development of a scapose stem which, with the leaf bases, 

 forms a bulb that may be small as in chives (Allium Schoenoprasum 

 L.), or very well developed as in the common onion (A. Cepa L.). 

 Other widely cultivated species are: A. sativum L., garlic; A. as- 

 calonicum L., shallot; and A. Porrum L., leek, in which a pro- 

 nounced bulb is nearly always absent. 



GENERAL MORPHOLOGY 



The Root System. — The root system is relatively shallow and 

 fibrous. New cycles of adventitious roots continue to arise from 

 the stem throughout the life of the plant, which radiate in all 

 directions but do not penetrate the soil to any great depth. 

 Sideris (i6) reports that 



"onion plants grown in water or in soil cultures produce two sets 

 of roots from the time of their germination to the completion of their 

 life cycle. The first set is produced at the time of germination and 

 functions during the period between germination and formation of 

 the bulb. . . . The second set is produced at the time of formation 

 of the bulb and later, and functions during the period between the 

 formation of the bulb and the death of the plant." 



Thompson (19) finds that the roots of onion seedlings attain a 

 depth of -L inches and a lateral spread of 3 inches within X5 days 

 after being planted; while in plants li inches tall with a base the 

 size of a lead pencil, the roots reach a depth of 4 inches. At 

 maturity, the majority of the roots are within 6 to 8 inches of the 

 soil surface and the greatest penetration does not exceed xo inches. 



179 



