42 TOPOGRAPHY OF CHLOROPHYLL APPARATUS IN DESERT PLANTS. 



chlorophyll tissue during the most of the year in Parkinsonia and Zizyphits 

 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 Celtis, 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 fovmd in stems 1 cm. in diameter. 



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

 is very similar to that of the leaf of the same plant. 



16. The following species were studied: Aster spinosus'Benth., Uaccharis 

 cinoryi Gray, Celtis pallida Torr. , Cercus gigantcus Englm., Condalia spatliu- 

 laca Gray, Covillea tridentata Vail, I^phcdra antisyphilitica C. A. Meyer, 

 roitqtiieria splcndcns Englm., Franseria dumosa Gray, Krameria canescens 

 Gray, Ktxberlinia spinosa Zucc., Olneya tcsota Gray, Parkinsonia aculeata 

 L., Parkinsonia tnicrophylla Torr., Parkinsonia torrcyana Watson, Prosopis 

 vc/iitina Wooton, Sa/i.v nigra Marsh,, Sainbucus mcxicana Presl., Zizyphus 

 parryi Torr. 



