142 Guayule. 



Description of Plate 29. 



1. Leptome region of hypocotyl shown in fig. 3. 



2. Leptome region of hypocotyl shown in fig. 4. 



3. Hypocotyl, irrigated seedling of very rapid growth. 



4. Hypocotyl, irrigated seedling of very slow growth. 



5. Pith, Cedros irrigated stem, showing sclerosed pith-cells. 



6. A few of these cells in detail. 



