42 TOPOGRAPHY OF CHLOROPHYLL APPARATUS IN DESERT PLANTS. 



chlorophyll 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 Ccltis, 4.1 in I\u-bcrlinia, 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 p- 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 steins 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!&&r\.tin.., liacc/iaris 

 cinoryi Gray, Ccltis pa/lida Torr., Cereus giganteus Englm., Condalia sf>atlni- 

 laca Gray, Coril/ca tridcnlatci Vail, Ephcdra antisyphilitica C. A. Meyer, 

 l : oii<[iih'i'ia splcndois Eng'lm., Franseria dumosa Gray, Krameria canes cens 

 Gray, Kceberlinia spinosa Zucc., Olncya tcsota Gray, Parkinsonia acnlcata 

 L., Parkinsonia micro frhylla Torr., Parkinsonia torrcyana Watson, Prosopis 

 I'clntina Wooto'n, Sali.\~ nigra Marsh,, Sainbnciis ine.vicana Presl., 



parry i Torr. 



