620 BRITTON: VEGETATION OF THE 
PLATE 27 
a. Transverse section of a portion of the root of Cyperus filiculmis, showing single 
vessel in the center and thick-walled endodermis. vw, vessel ; ¢, endodermis ; cov, cor- 
tex. >< 550. 
6. Section of small root of Sporobolus vaginacflorus, showing endodermis with 
inner walls mnch thickened, thick-walled pericycle and very large cortical cells. >< 175. 
¢. Transverse section of a portion of a large root of Sporobolus vaginacflorus, 
showing four large vessels in the central portion. 7, vessel; Z, pericycle ; ¢, endo- 
dermis with wall thickened but less so than in small root ; cor, cortex. > 175. 
d. Transverse section of the root of Andropogon furcatus, showing vessels, endo 
dermis, central and cortical tissues. c, central cells mostly filled with starch ; ¢, endo- 
dermis with inner walls of cells thickened ; cor, cortex ; v, vessel. >< 115. 
e. Gross appearance of rootstock of Andropogon furcatus, showing thickened 
nodes. Reduced. 
f. Transverse section of a portion of the root of Spartina cynosuroides, showing 
lacune. /, lacunes; 7, root-hairs. >< 70. 
PLATE 28 
a. Transverse section of small root of Salomonia biflora ( Polygonatum biflorum ) 
showing 6-rayed xylem with endodermal layer interrupted opposite the xylem points. 
Also the great development of water-holding cells in cortex. >< 70. 
6. Transverse section of a root of Trichostema dichotomum in which secondary 
thickening has taken place. The vessels are large and numerous. No sclerenchyma- 
cells in the cortex. > 70. 
c. Transverse section of secondarily thickened root of Polygonum Convolvulus. 
The vessels are extremely large. A few strengthening cells in the cortex.  79- 
d. Transverse sections of secondarily thickened root of Crotalaria sagittalis. The 
vessels are large and numerous, and sclerenchyma-cells are abundant in the cortex- 
33. 
