vi Table of Contents. 



CHAPTER V. ANATOMY AND HISTOLOGY Continued. 



Page. 



Age and structure in the seedling 104 



Epicotyl 105 



The definitive stem 107 



Primary structure 107 



Secondary structure 109 



Origin of the medullary and cortical stereome no 



Annular structure 114 



The effect of abundant water upon anatomical structure 116 



Relative volumes of cortex and wood 117 



Effect of various amounts of water of irrigation 121 



Effect of drought following irrigation 122 



Effect of irrigation on the physical characters of the wood 122 



The peduncle 124 



The leaf 125 



Cotyledons 125 



Prophylls 126 



The definitive leaf 126 



CHAPTER VI. THE RESIN-CANALS IN THE GUAYULE. 



The canal-systems 165 



Primary canals in the root and hypocotyl 165 



Primary cortical canals 166 



Medullary canals 1 69 



The canals in the leaf 171 



Primary canals in branches 171 



Secondary canals in root, hypocotyl, and stem 172 



Canals in the peduncle 172 



The canals in retonos 173 



The contents of the canals; their origin 174 



The role of resin 174 



Resin-content of guayule by analysis 175 



CHAPTER VII. THE ORIGIN AND OCCURRENCE OF RUBBER. 



Methods 176 



General distribution of rubber in the plant 177 



The appearance of rubber in richly loaded tissues 179 



Behavior of peridermal divisions toward rubber 179 



The development of rubber in the cell 180 



Centers of secretion 1 8 1 



Rate of rubber secretion relative to growth 183 



Rubber-content by chemical methods 185 



Variation in relative amount of rubber in field plants 187 



Relation of rubber and resin 188 



The significance of rubber 188 



Summary 190 



CHAPTER VIII. VEGETATIVE REPRODUCTION. 



Induced root-regeneration 193 



Propagation by cuttings 195 



CHAPTER IX. THE CULTIVATION OF GUAYULE. 



Forestal operations 199 



Present field operations 199 



Suggested rules of practice 200 



Harvesting period 202 



Reseeding barren ground 202 



Cultural operations 203 



Seed \ 203 



The raising of seedlings 203 



Irrigation 208 



Transplanting 209 



Harvesting cultivated guayule 210 



Catch crops 210 



Bibliography 2II 



