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TEXTBOOK OF BOTANY 



Fig. 119. Epiphytic bromelias on live oaks in southern Florida. Photo from New 



York Botanical Garden. 



the same green plant or those of other nearby plants. The haustoria em- 

 bedded in woody stems may survive from one season to another, and 

 from them the dodder plants propagate vegetatively each year. 



Internal structure of roots. A limited observation of root systems is 

 sufficient for one to see that roots are usuallv largest at or near their 

 junction with the base of the stem and gradually taper in size to slender 

 and tender tips. From these facts one may infer that the root tip is the 

 zone of growth in length. Since the older portion of a root toward its 

 base is the largest, there must be some means by which roots increase in 

 diameter. 



If a cross section of a young root of a tulip tree is compared with a 



