DALBEY: ANATOMY OF GRINDELIA. 33 



There are a few thick, bud-shaped hairs on the margin of 

 the leaf, which extend toward the apex, and project almost 

 parallel with the margin of the leaf (figs. 13, b, and 14, g). 



The chloroplast-bearing mesophyll cells are irregular in ar- 

 rangement, some patches extending from surface to surface 

 and others not (figs. 3 and 5). They vary from .006 mm. to 

 .011 mm. in width, and from .016 mm. to .030 mm. in length. 

 A single cell shows 8 to 16 chloroplasts of the usual type 

 (fig. 17, s). 



The leaf has a clasping base, and is entered by three vascu- 

 lar bundles. Near the base of the leaf, the tissue between 

 these three bundles is composed of water-storage cells (figs. 1, 

 a, and 7, i). 



In cross section the vascular bundles are seen near the cen- 

 ter of the leaf, midway between the upper and lower surfaces 

 (figs. 3, i, and 5, w). The number in one cross section varies 

 from 10 to 36. 



The marginal veins unite in the serrations and form a coal- 

 escent mass of tracheids (figs. 1, 13, c, and 14, i) . The tracheids 

 have bordered pits, and spiral thickenings (fig. 20, b and c) . 

 The xylem and phloem are about equal in amount in the larger 

 veins. They are separated by a layer of conjunctive parenchyma 

 varying from one to three cells in thickness (fig. 4, q) . The 

 number of tracheids found in a cross section of a single vascu- 

 lar bundle varies from 5 to 37, and in the larger veins wood 

 parenchyma and tracheal tissue alternate in radial rows, and 

 bast fibers subtend the base of each bundle (fig. 4). 



Resin ducts, on the average .028 mm. in diameter, are found 

 near the phloem. They are surrounded by from 7 to 12 se- 

 creting cells (figs. 3, I, and 5, y). 



The cells of the epidermis are rather thick-walled, and ap- 

 pear largest when seen from the surface (fig. 15, k) . The 

 outer walls are decidedly thickened, being on the average 

 .007 mm. thick. A cuticle layer .0045 mm. thick is sculptured 

 into irregular ridges, and in cross sections in places appears 

 to be striated. In addition to this, cutinization goes deeper 

 to the extent of .002 mm. in the walls of the epidermal cells 

 which join the water-storage tissue. 



A cuticle layer covers the walls of the guard cell where 

 they bound the stomata, and extends back over the inner 

 epidermal walls, thus lining the outer part of the stomatal 



