SPECIAL PART: THE CHLOROPHYLL APPARATUS. 7 



was determined by inspection only, and all chloroplastids that from com- 

 parison were seen to be normally colored were classed as being functional 

 and were considered as having adequate amounts of light and of air. 



The following plants were passed under observation during the course of 

 this study: Aslcr spinosus Benth.; Baccharis emoryi Gray; Celtis pallida 

 Torr.; Cerens gigantcus Englm.; Condalia spathulaca Gray; Coi'illca tridentata 

 Vail; J-'.plicdra antisyphilitica C. A. Meyer; Foitqtticria splcndcns Englm.; 

 Frcmseria dumosa (iray; Kirbcrlinia spinosa Zucc.; fCrameria ranescens Gray; 

 ()//t/-t'it It-sota Ciray; Parkinsonia antteata L.; Parkinsonia microphylla Torr.; 

 ParkiHsonia torrcyana Watson; Prosopis vclutina Wooton; Salix nig'ra Marsh. ; 

 Sd>i/l>ii(-i/s mcxicana Presl.; /.isy pints parry i Torr. 



SPECIAL PART: THE CHLOROPHYLL APPARATUS. 



ASTER SIMNOSUS; BACCHARIS EMORYI. (Fig. i.) 



These plants inhabit the wash along the river and the irrigating and 

 wayside ditches, where water is frequently to be found. Aster spinosiis is 

 an annual with perennial root; Haccliaris cnioryi is ])erennial. Both Aster 

 and Jiaccharis are usually devoid of leaves, but the young portions at least 

 are supplied with rudimentary ones. 



FIG. i. Baccharis emoryi: A, segment from transverse section of young 

 stem to show the character of cortical chlorophyll band (ch.b.); /?, sec- 

 tion of leaf, magnified as in A* 



Chlorophyll of the stem is confined to the cortex in both species and in 

 both the chlorenchyma is palisade. The palisade in the stems of each also 

 closely resembles that in the rudimentary leaves of the same species. This 

 similarity in the structure of the chlorophyll band* in the stem and of the 



*In all figures chlorophyll is indicated by stippling. 



