VEGETATIVE AND SEXUAL EEPKODUCTION 157 



spring 



and either becomes distended with reserve food or serves as an 

 attachment for scalelike leaves and roots. Buds spring from the 

 axils of the scale leaves as they do from the leaves of an ordi- 

 nary branch, and 

 these grow into 

 new bulbs or new 



Parent buib.,,^^ \\ . /AX. W areH . 1 . corms. Tubers, 



corms, and bulbs 

 are favorite repro- 

 ductive structures 

 of plants in dry 

 regions or in cli- 

 mates where a dry 

 season prevails for 

 a portion of the 

 year. When the 



^7 SeaSOll COmeS 



oil the aerial 2Teen 

 , . & . 



part of the plant 

 dies down, and the underground bulb, tuber, or corm is able to 

 live without perceptible injury from drought. These fleshy stems, 

 with great stores of food, have been changed and improved for 

 man's use by high cultivation 

 and selection. In nature their 

 production illustrates the abil- 

 ity of plants to adapt them- J (\^Parent corm- 



selves to various environmental 

 conditions by variation and 

 selection. 



FIG. 79. Bulbs of the garden tulip 



a, surface view of a large bulb, showing the origin of 



smaller bulbs in the axils of bulb scales ; b, sectional view 



of the same bulb, showing stem, roots, scales, and a lateral 



bulb (offspring) 



a, surface view of a large corm with 



smaller corms; 6, sectional view of the 



same corm 



TT A "\7TTQ 



FIG. 80. Corm of gladiolus 

 Ordinary leaves, such as 

 those of the cultivated begonia 

 of the greenhouses, may repro- 

 duce new plants vegetatively when properly treated. The leaves 

 are usually cut and placed in moist sand, when new plants spring 

 from the cut surfaces of the veins by budding. The buds take 



