158 Guayule. 



DESCRIPTION OF PLATE 37. 



1-5. Primary cortical canals. 



1. Endodermal origin in a young epicotyl. This canal has beqn rotated, but not 



displaced otherwise. 



2. Etiolated seedling-epicotyl. Lateral displacement, but not sufficient to mask 



its relation to the endoderm. 



3. Displacement sufficient to mask origin. 



4-5. First internode. An earlier and later stage in the derivation of the cortical 

 canal from the endodermis. The endodermal origin is masked by indefinite 

 character of endodermis. 



6-7. Later and earlier conditions of ventral foliar canal, xy indicates the position 



of the hadrome of the mid-vein. 

 8. Cortical canal in Parthenium incanum. The endodermal origin is clear. 



