40 TOPOGRAPHY OF CHLOROPHYLL APPARATUS IN DESERT PLANTS. 

 Measurements on the chlorophyll band. 



PERSISTENCE OF CHLOROPHYLL IN THE WOODY CYLINDER. 



Chlorophyll in the woody cylinder is a striking characteristic of young 

 Parkinsonia and Prosopis branches especially, and is found in nearly all of 

 the other desert perennials. Compared to the chlorophyll of the cortex, 

 however, it is likely of little profit to the plant, for the reason that it 

 disappears early from the stem. How lon.y it persists was not learned in 

 any case, since the plants studied did not exhibit annual rins's, or in any 

 other way give a clue as to the rapidity of growth. 



The subjoined table gives the character of the branch at a time when 

 the chlorophyll for the most part had already left the woody cylinder. The 

 measurements were made on the disappearance of chlorophyll. 



