140 Guayule. 



Description of Plate 2S. 



1. Irrigated plant, stem 1 year's growth. 



2. Field plant, stem 2 years' growth. Note width of parenchyma rays and depth 



of cortex. (Figs. 1 and 2 are drawn to same scale.) 



3. Hypocotyl, field seedling less than 1 year old. 



4. Cortex of hypocotyl after secondary enlargement. Transverse section. 



5. Cortex of root; tangential section. 



