40 TOPOGRAPHY OF CHLOROPHYLL APPARATUS IN DESERT PLANTS. 

 Measurements on the chlorophyll band. 



Species. 



Aster spinosus 



Baccharis emoryi 



Celtis pallida 



Do 



Cereus giganteiis 



Condalia spathulaca 



Do 



Covillea trideiitata 



Do 



FoLiquieria splcndens 



Do 



Koeberlinia spino.sa 



Do 



Kranie>-ia canescens 



Do 



OIneya tesota 



Do 



Parkinsonia microphylJa. 



Do 



Do 



Parkinsonia torreyana.... 



Do 



Prosopi.s velutina 



Do 



Zizyphus parryi 



Do 



niamPtPr I Width Of Depth of 

 o^h^Sir. |cb.oroP^;yli;eh.o3hy,, 



25.6 

 25.6 



144 

 1 12 



83.2 

 60.8 



160 

 83 

 130 

 246 

 144 

 224 



3- 

 160 

 57-6 

 64 



19.2 

 16 



96 



108. S 



5«' 



80 



19.2 



48 



80 

 498 

 1 162 



80 



64 



18.8 



32 



38-4 



64 



83 

 144 

 130 



64 

 128 



48 



32 



19.2 



41.6 



PERSISTENCE OF CHLOROPHYLL IN THE WOODY CYLINDER. 



Chlorophyll in the woody cylinder is a striking- characteristic of young- 

 Pa: r/^/?«<?w/rt and Prosopis branches especially, and is found in nearly all Of 

 the other desert perennials. Compared to the chlorophj-ll of the cortex, 

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

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

 any case, since the plants studied did not exhibit annual rings, or in any 

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



The subjoined table g'ives the character of the branch at a time when 

 the chlorophyll for the most part had already left the woody c.\'linder. The 

 measurements were made on the disappearance of chlorophyll. 



