134 Guayule. 



DESCRIPTION OP PLATE 25. 



1-6. Primary endodermal resin-canals of the hypocotyl. 



1. Cell lineage (diagrammatic). 



2. A not infrequent but abnormal behavior. 



3. Definitive condition, as regards cell- walls. 



4. Definitive condition after growth and readjustment. 



5. Endodermic stereids adjacent to canals. 



6. Stereids (pericyclic ?) just within canal in stele. 

 7-10. Transverse sections; hypocotyl. 



7. Field seedling, 1.8 mm. diameter. 



8. Irrigated seedling of slow growth. Secondary splitting apart of wood cylinder. 



9. Etiolated seedling 2 mm. diameter. 



10. Etiolated seedling 2 mm. diameter. Hypocotyl through cotyledonary collar. 

 Secondary hadrome of cotyledonary median traces is morphologically 

 cauline and distinct from primary tissue. /. c. t., Lateral cotyledonary 

 trace passing out from the stele. 



ioa, 1 06. Cotyledonary, median traces at another level. 



