42 TOPOGRAPHY OF CHLOROPHYLL APPARATUS IN DESERT PLANTS. 



chloro]:>hyH tissue during' the most of the year in Parkinsonia and Zizyphus 

 Parryi. 



12. The volume of the chlorophyll band for a unit stem has a value of 

 1 in Celtis, 4.1 in Ka-berlinia, 4.7 in Parkinsonia, and 5.7 in Prosopis. The 

 least volume occurs in evergreen forms; the greatest in plants which depend 

 in part or entirely on it for photosynthesis. 



13. The thickest chlorophyll band is in Parkinsonia, which is 246 /^ in a 

 stem 4.9 cm. in diameter. The thinnest band is in Ccltis, which is 25 /* in 

 in a stem 1 cm. in diameter. 



14. Chlorophyll usually disappears early from the woody portion of the 

 stem, but in Parkinsonia it may be found in stems 1 cm. in diameter. 



15. When the chlorophyll band is palisade, the character of the palisade 

 is ver\- similar to that of the leaf of the same plant. 



16. The following species were studied: Aster spinosiis Benth., Baccliaris 

 emoryi Gray, Celtis pallida Torr., Cereics giganteus Englm., Condalia spathu- 

 laca Gray, Covillea tridentata Vail, Ephedra antisyphilitica C. A. Meyer, 

 Fouquieria splendens Englm., pyanseria dumosa Gray, Krameria canescens 

 Gray, Ka'berlinia spinosa Zucc Olneya tcsota Gray, Parkinsonia aciileaia 

 L., Parkinsonia niicropliylla Torr., Parkinsonia torreyana Watson, Prosopis 

 veliitina Wooton, Salix nigra ]\Iarsh,, Sanibucus mexicana Presl., Zizyphus 

 parryi Torr. 



