THE BUD 



19 



flattened out. The pericambium has a tendency to start division into 

 an inner and outer layer. The outer layer becomes a cork cambium 

 (phellogen) surrounding the bundle inside 

 the endodermis It cuts off cork tissue 

 on its outer face, hence all liquid material 

 is prevented from filtering in and cortex 

 including endodermis, as well as the epi- 

 dermis, shrivel and dry up and separate off 

 at the age of two to three months. The 

 cork cambium (phellogen) may lay down 

 secondary cortex internal to itself and ex- 

 ternal to the pholem. 



Patches of cells of the inner iayer of 

 pericambium divide rapidly and are called 

 interfascicular cambium. These join the 

 intrafascicular cambium to form a con- 

 tinuous cambium ring which then cuts 

 off additional secondary xylem on its inner 

 face and secondary phloem on its outer 

 face pushing inward the first-formed or 

 protoxylem and outward the first-formed 

 or protophloem. 



The Bud 



Buds are rudimentary stems with rudi- 

 mentary leaves compactly arranged upon 

 them. 



The COTYLEDONS and plumule repre- 

 sent the first bud on the initial stem or 

 caulicle. 



Scaly buds are such as have their 

 outer leaf rudiments transformed into 

 scales, often coated with a waxy or resi- 

 nous substance without and a downy lining 

 within, to protect them from sudden 

 changes in climate. Ex. : Hickory. 



Fig. 14. — Cross-section of a 

 young root of Phaseolus multi- 

 florus. A, pr, cortex; m, pith; 

 X, stele (ail tissues within the 

 endodermis collectively); g, g, 

 g, g, primary xylem bundle; b, 

 b, b, b, primary phloem bundle. 

 B, cross-section through older 

 portion of root of the same 

 plant, b', b', Secondary bast; 

 k, k, periderm. The remaining 

 letters stand for the same tis- 

 sues as in A. Notice that the 

 cambium has laid down medul- 

 lary rays in front of the primary 

 xylem, but has made secondary 

 xylem behind the primary 

 phloem. {From Steiens after 

 Vines.) 



Naked buds are those whose leaf rudiments are destitute of cover- 



ings. 



