10 



TOPOGRAPHY OF CHLOROPHYLL APPARATUS IN DESERT PLANTS. 



stant relation was not learned. In a branch 1.6 cm. in diameter, as well 

 as one 1 cm. in diameter, the chlorophyll was confined to the cortex. 

 The following: measurements were made: 



CoNDALiA SPATHULACA. (Plate 2, A, and fig. 4.) 



The plant from which the branch studied was taken is g-rowin.q- by the 

 Hospital Road near the northeast corner of the Laboratory domain. The 

 shiiib is about 1.5 m. high and is a very vig-orous one. 



vSections were made at the fol- 

 lowing- distances from the tip: 

 2, 5, 20, 35, 65, 95 cm. These 

 were 1.5, 2, 4, 7.5 mm. and 1.2, 

 1.7 cm. in diameter, respec- 

 tively. 



A cross-section of a young 

 branch 1.5 mm. in diameter and 

 2 cm. from the tip shows the 

 following leading structural 

 characters: An epidermis with a 

 thin cuticle bounds the stem. 

 Within this is a hypodermal por- 

 tion three cells thick, and within 

 this, again, is a collenchyma-like 

 tissue about as thick. The 

 chlorophyll band, about three 

 cells wide, lies immediately within the last-mentioned tissue and occupies 

 the central portion of the cortex. A relatively narrow inner cortical portion 

 separates the chlorophyll band from the cambium. This inner part consists 

 of a discontinuous hard-bast ring and thin- walled parenchyma . The former 

 abuts on the chlorenchyma. The wood and the pith present no character- 

 istics of interest in the present connection. In addition to the chlorophyll 

 band, chlorophyll occurs also in most of the inner cortical parenchyma, in 

 the medullary rays of the wood, and in the outer pith-cells. 



Fig. 



4. — Condalia spathulaca: Section from 

 a branch 2 mm. in diameter. 



