TABLE OF CONTENTS. 



Page. 



Preface iii 



List of plates vii 



Chapter I. Historical Account. 



Original discovery and description 3 



The vulgar name 4 



Primitive and later uses 5 



History of manufacture 7 



Methods of extraction 8 



The natural supply of shrub ro 



Attempts at culture 12 



Chapter II. The Environment. 



Geographical distribution 13 



Altitudinal distribution 13 



Climate 14 



Rainfall 14 



Air-temperatures 15 



Soil-temperatures 18 



Soil-moisture 19 



Relation of rainfall and temperature to growth 20 



Relative humidity 21 



Topography and soil 23 



Density of growth 25 



Biotic relations 35 



Chapter III. Description of the Guayule. 



Seed 46 



Seedling 48 



The mature plant 50 



Root-system 50 



Retonos 51 



Method of branching 54 



Biotypes 55 



Size 56 



Surface characters of the stem and method of determining age 57 



Field plants 57 



Irrigated plants 58 



The leaves 58 



The inflorescence and the flowering period - 59 



The production of seed 60 



Chapter IV. Reproduction. 



Methods of reproduction 61 



Retonos, normal and induced 61 



Seed 68 



Rate of reproduction and of growth 75 



Rate of growth during germination 75 



Rate of growth in maturer plants beyond the seedling stage 79 



Rate of growth in terms of stem-length 79 



Rate of growth in earlier years after germination 79 



Rate of growth in medium-sized plants 81 



Rate of growth in irrigated plants 84 



Field plants 85 



Chapter V. Anatomy and Histology. 



Root 9 



Primary structure 90 



Secondary structure .' 9 



Hypocotyl 96 



Primary structure 96 



Secondary structure 99 



Later secondarv structure 101 



