PLATE XLII. 



Townsendia exscapa. 



Fig. 27. Diagrammatic drawing showing the distribution of water- 

 storage cells as seen in cross section of a leaf: a, veins; b, 

 water-storage cells. 



Fig. 28. Palisade cells bordering on water-storage cells: A, water- 

 storage cells; B, palisade cells; a, chloroplasts found in water- 

 storage cells. X 650. 



Fig. 29. Palisade cells bordering on the veins: A, palisade cells; B, 

 border parenchyma cells; C, tracheids. X 650. 



Fig. 30. Palisade cells bordering on water-storage cells and storage 

 tracheids: A, water-storage cells; B, chloroplasts found in 

 water-storage cells; C, water-storage tracheids; D, palisade 

 cells. X 650. 



Fig. 31. Palisade cells bordering on water-storage cells, which in turn 

 border on veins: A, water-stoi'age cell; B, chloroplasts; C, 

 tracheids; D, border parenchyma cells. X 650. 



Fig. 32. Palisade cells bordering on spongy parenchyma cells: A, pali- 

 sade cell; B, spongy parenchyma cell; C, intercellular spaces. 

 X 650. 



Fig. 33. Water-storage tracheids as they appear at the ultimate ends of 

 the veins: A, veins; B, water-storage tracheids. X 650. 



Fig. 34. Water-storage tracheids as they appear in other places in the 

 leaf: .4, ordinary tiacheids; /?, water-storage tracheids. 

 X 650. 



Fig. 35. Stomata, suiface view, x 650. 



Fig. 36. Stoma, as seen in cross section of the leaf, x 650. 



